SU1210120A1 - Universal digital photographic exposure meter - Google Patents

Abstract

The invention relates to photographic equipment. The aim of the invention is to increase the usability of the photoexposure meter. There is no special integrator in the device — its role is played by the photodetector 1 and the integrating capacitor 3. When an additional photodetector 10 is applied to the flash light pulse, the strobe-pulse generator 9 closes. The voltage of capacitor 3 as the final result of the measurement, digitized, is stored in the decoder counter 5 and is displayed by the indicator 7 as the size of the relative aperture of the lens and is stored until the counter is set to zero by 14. The photo imager allows you to determine the exposure when taking photos - the value of the relative aperture of the lens at a given shutter speed and the sensitivity of a negative photographic material - when illuminated with both constant and pulsed light, as well as with a combination of last. 1 il. % (L with s

Description

The invention relates to photographic equipment, in particular, to devices for determining exposure during photographing.

The purpose of the invention is to increase the usability of the photoexposure meter.

The drawing shows the principle scheme of the photoexposure meter.

The proposed photoexpononometer contains a photodetector 1, a sensitivity switch 2 of the film, and integrating capacitors. 3, operational amplifier 4, counter-decoder 5, digital-to-analog converter 6 digital indicator Y key 8, strobe-pulse generator 9, additional photodetector 10, start button 11, shutter switch 12, time setting 13 Elements, button 14 Installing to O, resistors 15 and 16 are the digital-to-analog converter divisors, which are decoupled. Dio, dy 1 7.

The first pin of the photodetector 1 is connected to the non-inverting input of the operational amplifier 4. The output is generated: the gate 9 of the gate-pulse is connected to the control input of the switch 8 connected in parallel with the integrating capacitor 3,

A start button 1i is connected in parallel to an additional photodetector 10, the first output of which is connected to the input of the strobe-pulse generator 9. The second terminals of the photoreceivers 10 and 1 are connected to the power supply bus.

Non-inverted 11: the input of the operational amplifier 4 is connected via an integrating co.densor 3 to a common source-decoder bus-5, the bit outputs of which are connected to the corresponding bit inputs of the indicator 7 and the digital-to-analog converter .65 output connected to the inverting input of the operational amplifier 4 .

Switches 2 and 12 serve as the setting of the required sensitivity of the film and the required duration of the strobe pulse.

Button 4 serves to reset the indicator 7 and reset the counter-decoder 5.

Resistors 15 and 16 form a voltage divider on the basis of which a digital-to-analog converter 6 is made.

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Diodes 17 are designed to isolate the effects of the counter-decoder outputs to one another.

The device works as follows.

in a way.

In the initial state, the integrating capacitor 3 is discharged through the closed key 8, since x the gate stator pulse 9 is located

 relsime expect. The decoder counter 5 is set to the zero state by button 14. This state is displayed by the digital indicator 7. The inverted input of the comparator 4 from the digital output of the converter 6 receives the first OPORT level, the corresponding counter zero. - decoder. When an additional photo exposure is applied to the DO, a light flash pulse of the flash or a short circuit of the start button I 1 by the operator starts the strobe pulse generator 9, the output signal of which

opens key 8 ". When integrated, capacitor 3 is charged by the current of the receiver, proportional to the illumination of its working surface,. As the capacitor 3 is charged, the voltage on the node is limited to Hj when it is compared with the first basic level of the digital-to-analog converter 6, the operation: the first device 4 changes its state

the opposite. The voltage drop at the output of the operating ycj-shih gel 4 translates the counter-decoder 5 into a light (single) state, in which

encoder change information on

the indicator 7 and is fed to the i.ksertiruyushchy input of the comparator 4 through the digital-to-analog converter 6 ,, the second reference voltage level “difference

from the previous one. The operational amplifier 4 is then switched to the initial (floating) state.

Further growth: ... zhenig.d: on capacitor 3, lead to the closure of the described process, each subsequent state of the counter-decoder 5 corresponds to

The next reference level is the NIN digital-analogue converter 6, which differs from the previous one in -G 1 ,, 41 times.

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The indicator on the digital indicator 7 changes accordingly and displays, with each subsequent state of the counter, decreasing the relative aperture of the lens by half the standard range of relative aperture values.

The voltage rise on the capacitor 3 stops at the moment of termination

NEW impulse (in the absence of software

or at the end of the strobe pulse generator 9.

As follows from consideration of the electrical functional circuit of the photometer, the proposed device does not have a special integrator — the photodetector and the integrating capacitor 3 play a role,

The voltage across the capacitor 3, as the final measurement result, digitized, is stored in the decoder counter 5 and is displayed by the indicator 7 as the size of the relative aperture of the lens. This information is stored until the counter is set to the zero state by the button 14.

The duration of the strobe pulse generated by the generator 9 determines the time during which the charging of the integrating capacitor 3 takes place.

The duration of the strobe pulse is determined by the nominal time of the driver elements 13 and the position of the 12 shutter switch. The scale of the latter corresponds to the standard range of arms. Since, due to the irreplaceable quality, the required exposure is different for the pulsed and constant light sources, the duration of the strobe pulse, the capacitance of the integrating capacitors 3 and the slope of the photodetector's lux-capacitance characteristics must be strictly consistent with each other and with the intervals of the reference levels,

Thus, the pradhshgayemy photoexposure meter allows you to determine the exposure during photography to the value of the relative aperture of the object at a given shutter speed and sensitivity of the negative photographic material, both under constant light and humid lighting, as well as a combination of the latter, each

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from two modes: either in the mode of;; Measurement of illumination at the location of the shooting, or in the mode of measuring the brightness of the subject For measurements in the first mode, the photodetector is closed by a diffuser providing the required proportionality between illumination and object brightness. The light synchronization of the control device (the start of the strobe pulse generator) creates additional convenience when using the photoexposure meter, since it does not require a wired connection between it and the photo flash.

The use of the invention will make it possible to create a simple and convenient mass device that equally satisfies the requests of both professional photo professionals and amateurs, having a cost at or even lower than the cost of photo exposure meters for working with constant illumination.

Claims (1)

Invention Formula A universal digital photoexponometer containing a photodetector, an integrating capacitor, an operational amplifier, a start button, a strobe pulse generator, a power source, and a digital indicator, the first output of the photodetector connected to a non-inverter thin input of the operational amplifier, and the encoder of the strobe pulse connected to the control a key input connected in parallel with an integrating capacitor, characterized in that, in order to enhance the convenience of operation of the photoexposure meter., an additional photo is inserted into it receiver, counter-decoder and digital-analog converter; the start button is connected in parallel with an additional photodetector, the first terminal of which is connected to the input of the strobe pulse generator, the second terminals of the photoreceivers are connected to the power supply bus, the non-inverting input of the operational amplifier is connected via an integrating capacitor c. common power supply bus, the output of the operational amplifier is connected to the counting input of the counter-decoder, the bit outputs of which are connected to the corresponding bits