we're gonna use the acoustic version of lenses to firmly image it directly let's just assume there's a target you know a piece of tissue we want an image we fire a light pulse to illuminate the tissue to generate photo acoustic waves and then we use this focused ultrasound transducer to receive the signals and you're gonna get a time trace like this so this is your time axis you get a voltage like this you'll see a spike corresponding to where the target is so if this guide is deeper then this spike is gonna appear later if you have