detection of small volume drops down to 1 pl for the purpose of this invention a standard normal distribution is assumed for noise the noise is defined as four times the standard deviation 4 u03c3 of the signal obtained in the absence of ink drops the signal is defined as the peak to peak amplitude obtained in the presence of ink drops as snr is often measured in decibels db the following equation yields the decibel equivalent of changes in snr achieved with the present invention the use of apertures of width from about 0 1 to 2 mm improves snr to a range of 3 to 20 db improvement in signal to noise can also be achieved by firing multiple ink drops from a given ejection port and averaging the detection response this averaging builds up the signal while reducing the noise however such averaging also results in an increase in the overall detection time and lowered printer productivity with the present invention the increased signal to noise from the use of apertures can be utilized to reduce or eliminate signal averaging which will lower drop detection time and hence increase the efficiency of the detection process a further benefit of the enhanced signal to noise is reduced waste of ink for drop detection as fewer ink drops are utilized for detection the use of multiple and or alternate light sources and detectors can be used to further expand the capabilities of the drop detector to capture additional information regarding the ink drops an alternative embodiment of the present invention employing multiple light sources and multiple detectors is schematically depicted in fig4 there is a first collimated light source 30 and a second collimated light source 32 that are operated in conjunction with a.