A flow measuring method for the optical measurement of time variable flow parameters of a fluid flowing through a closed cross-section having at least one light source and having at least one sensor unit by which particles present within a measurement plane in the fluid are detected, wherein - at least one measurement plane and the particles present therein are illuminated by the light source; wherein - the particles are imaged on the sensor unit, and characterized in that - the sensor unit has a CMOS array detector having a directly connected FPGA and with the sensor unit being provided with at least two or with a plurality of individual detectors (12a, 12b, 12c, 12b) by which sensor signals relating to picture elements and/or picture lines are output; and in that - the sensor signals relating to picture elements and/or picture lines are converted continuously and in real time by means of the sensor unit by means of spatial filtering technology into at least one speed profile while omitting buffering; - the sensor unit continuously calculates flow parameters in real time from the time dependent speed profile comprising at least two of the following parameters: volume flow, accumulated flow amount, flow profile, turbulent/laminar flow state, degree of turbulence, spectrum of turbulence, spin; - the sensor unit continuously calculates and outputs with time resolution in real time one or more integral flow state parameters; - with the sensor unit and the field programmable gate array having a processing unit connected downstream by which the speed profiles are processed as integral flow parameters by the processing unit on the basis of the integration and weighting of the picture elements and/or picture lines by the FPGA and are output by an output module as an output signal. - at least one measurement plane and the particles present therein are illuminated by the light source; wherein - the particles are imaged on the sensor unit, and characterized in that - the sensor unit has a CMOS array detector having a directly connected FPGA and with the sensor unit being provided with at least two or with a plurality of individual detectors (12a, 12b, 12c, 12b) by which sensor signals relating to picture elements and/or picture lines are output; and in that - the sensor signals relating to picture elements and/or picture lines are converted continuously and in real time by means of the sensor unit by means of spatial filtering technology into at least one speed profile while omitting buffering; - the sensor unit continuously calculates flow parameters in real time from the time dependent speed profile comprising at least two of the following parameters: volume flow, accumulated flow amount, flow profile, turbulent/laminar flow state, degree of turbulence, spectrum of turbulence, spin; - the sensor unit continuously calculates and outputs with time resolution in real time one or more integral flow state parameters; - with the sensor unit and the field programmable gate array having a processing unit connected downstream by which the speed profiles are processed as integral flow parameters by the processing unit on the basis of the integration and weighting of the picture elements and/or picture lines by the FPGA and are output by an output module as an output signal.