DEVICE FOR COMPENSATION OF SHADOW SIGNAL FROM MULTIPLE-ELEMENT PHOTODIODE RECEIVERS Russian patent published in 1998 - IPC

FIELD: optical-electronic instruments. SUBSTANCE: device has multiple- element photodiode receiver 1, first matching amplifier 2, analog-to- digital converter 3, calculation unit 4, request unit 5, first and second multiplexers 6 and 7, address counter 8, memory unit 9, digital-to- analog converter 10 and second matching amplifier 11. First stage of shadow signal compensation involves storing two bias samples E_bias.1= 0 and E_bias.2= E_bias.max/2 to memory unit 9 and reading two shadow signal arrays UT₁[I] and UT₂[I]. These values and arrays are used by calculation unit 4 for calculation of array of bias voltage samples for each element of receiver 1 providing that shadow signals at input of analog-to-digital converter 3 are greater than lower threshold of input voltage of this analog-to-digital converter by given value U_o. This calculation conforms to equation: (1). Calculated array of samples is stored in memory unit 9, then corresponding shadow signal samples array UT₃[I] is read. Minimal level shadow signal samples array UT₃[I] and maximal level samples array UT₁[I] are used for calculation of bias voltage array E_bias.0[I] providing that average value of shadow signals of all elements of receiver 1 at output of analog-to-digital converter 3 is equal to zero. Calculation uses equation (1) using substitutions U_o= 0 and UT₂[I] = UT₃[I]. When samples array E_bias.0[I] has been stored to memory unit 9, samples of shadow signal of receiver 1 are equal. Equality of amplitudes of samples of read shadow signal is provided application of signal of alternating bias voltage during reset. Alternating constituent of bias voltage conforms to inverse function of shadow signal of receiver 1 up to scaling factor. Bias voltage level at input of first matching amplifier 2 and calculation of bias voltage using equation (1) leads to equality of constant level of shadow signal and lower threshold of analog-to-digital converter. This results in zero level of digital form of shadow signal at output of analog-to-digital converter up to error in calculation and sampling. EFFECT: increased precision of shadow signal compensation. 5 dwg