Coherent optical sensor with sparse illumination

A system for a target image reconstruction, comprising:

• a stepped frequency transmitter configured to emit stepped frequency waveforms having different constant frequencies at different periods of time;
• a modulator configured to modulate the stepped frequency waveforms-into frequency ranges, each of the stepped frequency waveforms-having a first frequency and a second frequency, wherein each of the stepped frequency waveforms¬is increased from the first frequency to the second frequency based on a range function, wherein the arrangement of the modulated stepped frequency waveforms has a sparsity factor, wherein the sparsity factor is defined as a number of wavelengths multiplied by a bandwidth per wavelength, divided by a total measurement bandwidth, wherein the sparsity factor is determined so as to be less than 1;
• a lens or antenna configured to transmit the modulated stepped frequency waveforms continuously to a target and accepting reflection of the modulated stepped frequency waveforms reflected from the target;
• a mixer configured to interfere the modulated stepped frequency waveforms and the reflection of the modulated stepped frequency waveforms to produce beat signals of interferences between the modulated stepped frequency waveforms and the reflection of the modulated stepped frequency waveforms;
• and
• a signal processor configured to reconstruct an image of the target from the beat signals.