charge carriers created by light incident on the exposed semiconductor are collected with the electrodes fig6 shows a plurality of inter digitated electrodes or fingers where the finger width d 1 and finger spacing d 2 of the electrodes largely determine the device characteristics such as responsivity bandwidth and inter electrode capacitance because of the low inter electrode capacitance msm detectors are capable of detecting multi ghz amplitude modulated optical signals a characteristic of particular importance for ladar applications is a voltage variable responsivity that can be modulated at microwave frequencies to mix or downconvert light signals that are amplitude modulated at microwave frequencies a simplified diagram of a time multiplexed arrangement for focal plane arrays is shown in fig9 here voltages representing current or charge proportional to the amount of light power or energy impinging on a detector pixel are fed into high speed electronic switches 331 332 and 333 to read out these voltages the switch 331 for the first row is closed and the switches for columns a b and c are sequentially closed and opened while an analog to digital converter samples the voltages at the appropriate times this same process is repeated for the second and third rows to create a complete image the digitized data is then displayed or stored for ordinary 30 hz video frame rates this technique is adequate however for very high frame rates of for example 1000 to 10 000 hz this technique may become difficult and expensive to implement in using ladar systems frame rates beyond 10 000 hz may be encountered as.