Optical processing

A method of operating a qPCR instrument having a plurality of optical channels, the instrument including:

• a fluorescence excitation source;
• a fluorescence detector having a signal output;
• an electronic analogue signal amplifier having an input coupled to said fluorescence detector signal output;
• and
• an analogue-to-digital converter (ADC) having analogue input coupled to an output of said analogue signal amplifier;
• the method comprising:
• calibrating said optical channel by adjusting an electronic gain of said electronic analogue signal amplifier;
• storing a calibration value of said electronic gain in non-volatile memory;
• applying automatic gain control (AGC) to an analogue electronic signal path of an optical channel during qPCR, wherein said AGC includes digitally determining a numerical gain value for said AGC;
• determining a digital fluorescence level signal by scaling a digitized fluorescence signal from said optical channel by both said calibration value of said electronic gain and said determined numerical gain value for said AGC, wherein the method further comprises:
• determining digital scaling factors for said optical channels for scaling digital outputs of the ADCs of the channels to provide substantially the same digital fluorescence level signal output from each said channel for the same level of detected fluorescence;
• and
• storing in said non-volatile memory a combination of said digital scaling factors and initial calibration values of said electronic gain for said plurality of optical channels.

A quantitative PCR (qPCR) instrument for combined qPCR and dissociation and/or association curve analysis, the instrument having a plurality of optical channels, wherein each optical channel comprises:

• a fluorescence excitation source;
• a fluorescence detector having a signal output;
• an electronic analogue signal amplifier having an input coupled to said fluorescence detector signal output;
• an analogue-to-digital converter (ADC) having analogue input coupled to an output of said analogue signal amplifier;
• and
• a quantified automatic gain control (AGC) loop configured to apply automatic gain control (AGC) to an analogue electronic signal path of said optical channel during qPCR, wherein said AGC includes digitally determining a numerical gain value for said AGC;
• and
• wherein the instrument further comprises:
• a digital signal processing system configured to:
• calibrate said optical channel by adjusting an electronic gain of said electronic analogue signal amplifier;
• determine and store a calibration value of said electronic gain in non-volatile memory;
• determine a digital fluorescence level signal by scaling a digitized fluorescence signal from said optical channel by both said calibration value of said electronic gain and said determined numerical gain value for said AGC;
• determine digital scaling factors for said optical channels for scaling digital outputs of the ADCs of the channels to provide substantially the same digital fluorescence level signal output from each said channel for the same level of detected fluorescence;
• and
• store in said non-volatile memory a combination of said digital scaling factors and initial calibration values of said electronic gain for said plurality of optical channels.