SU447576A1 - Luminous flux measurement method - Google Patents

Description

I

The invention relates to photometry, i A method for measuring weak photocurrents is known, in which a photovoltaic photosensitive capacitance is introduced into one of the arms of a balanced AC bridge powered by a constant frequency generator; the shoulders of the bridge adjust to the frequency of the power generator; measured luminous flux modulate

puller and affect them on p-ti

 transition of the photosensitive element.

; The unbalance signal obtained in the bridge diagonal is amplified, detected,

 amplified again and fed to a synchronous detector. Luminous flux

; determined by the value of direct current

at the output of the synchronous detector.

The accuracy of measuring the luminous flux in a known manner and the range of measurements covered by it in the region of weak radiation asHciaT from temperature fluctuations around the medium, from the instability of the parameters of photosensitive elements, their variation, the nonidentity of their themes, temperature and time characteristics.

the accuracy of the amplitude measurements of low-frequency signals, the presence of electrical noise at the measurement site and the level of the signal induced by them, and a number of other factors that directly affect the accuracy and magnitude of the lower measurement threshold.

The purpose of the invention is to expand the measurement range to the region of weaker

0 radiation and improving the accuracy of measuring scientific research institutes.

The delivered pell is achieved by the fact that the photosensitive element with p-tl

6, a transition is introduced into the auto-oscillation circuit of electrical oscillations, modulating the autogeneration frequency with a luminous flux,: mix the resulting frequency-modulated signal with the same signal, kept for half the frequency period; modulation, from the total emission fluctuations; The oscillations with a beat frequency and by the values of this frequency are determined by the presence and magnitude of the light flux.

S

The drawing shows a block diagram

yCTpoiScTBa that implements the described method, where j

one . modulator; 2 photosensitive tfbifi element with p-fL junction; 3 - device autogeneration of high frequencies; 4 buffer cascade; 5 - delay line (memory); 6 - amplifier 7 - mixer; 8 - detector; 9 - filter; , 10 - frequency meter; 11 - the executive mechanism.

In the complete position of the p-tl junction of the photosensitive element 2, the frequency of the autogeneration of the autogeneration device 3 is equal to f. ; in clarified - f p

Since the input I of the mixer 7 signal with

altered due to exposure

p (at the moment on the p-P transition frequency

open the SBe1Yuvym modulator of the photosensitive element) comes earlier, the person went to the input AND (for the delay of the delay line 5), then the mixer 7 beats two high-frequency signals of the Signal

It clarifies the position of the transition of the transition and comes from the avhagen-device; walkie-talkies at the present moment, and delayed: by the delay line of the signal with frequency f ,,

corresponding to the previous one; the darkened transition position. In this case, the output of the filter 9 to the input of the frequency meter 10 receives a signal with a beat frequency equal to Hz f fp. If the delay time is half of the light modulation period, then the frequency Hz continuously goes to the input of the frequency meter, which value light flux. If necessary, run the automation systems, the signal from the filter 9 is fed to the actuator 11.

 The described method allows measurements on conventional, serially produced photodiodes, with the aid of which; can be obtained frequency generation,; measured by megahertz and tens of megs

0 hertz, and thereby increase the speed of the equipment. The described method can be used for photoelectric inspection of moving surfaces, - when measuring the thickness of layers of various

5 materials for photoelectric control of the geometrical dimensions of products, degrees of their processing, etc.

Subject invention

The method of measuring the luminous flux, consisting in the impact of the modulated light on the pn junction of the photosensitive element and measurement

5 of its parameters, about the fact that, in order to expand the measurement range to the region of weaker radiation and increase the measurement accuracy, the light is a sensitive element with a p-tv junction

0 is introduced into the autogenerating circuit of electrical oscillations, modulating the autogeneration frequency with a luminous flux, mixing the received frequency-modulated signal with the same signal halted

the period of the modulation frequency, from the total oscillations, the oscillations with the beat frequency are selected and the presence and magnitude of the light flux is determined from the value of this frequency.