Related by context. Frequent words. (Click for all words.) 60 laser beam 60 infrared 59 sensor detects 57 infra red 57 laser beams 57 infrared laser 57 sensor 56 infrared rays 54 infrared sensor 54 laser pulse 53 homing device 53 X ray beam 53 electromagnetic waves 52 detector 52 infrared radiation 52 infrared camera 52 motion detector 52 beep 52 radiation detector 52 photodetector 51 electrical impulses 51 strobe light 51 infrared sensors 51 reticule 51 beeps 50 audible alarm 50 fluorescent dye 50 CCD camera 50 laser 50 electromagnet 50 dosimeter 50 directional antenna 49 omnidirectional 49 infrared IR 49 monocular 49 laser pulses 49 electromagnetic 49 photon 49 eyepiece 48 electrical currents 48 detects 48 electrical pulses 48 electrodes 48 terahertz radiation 47 inertial navigation 47 ultrasonic 47 digital readout 47 tracer 47 pulse generator 47 photons 47 sensors 46 optically 46 bioluminescent 46 piezo 46 thermistor 46 tuning fork 46 transmitter 46 reflector 46 brainwaves 46 imager 46 strobe 46 flashlight 46 particle beam 46 transmissive 46 preprogrammed 46 flapping wings 46 attenuator 46 vibrates 46 suction cup 45 parallax 45 spectrometer 45 stylus 45 illuminator 45 ultra violet light 45 photonic crystal 45 servo motors 45 toggle switch 45 sine wave 45 interferometry 45 interferometer 45 meteoroid 45 Photons 45 photodiode 45 UV light 45 cloaking device 45 fluorescent 45 electrode 45 infrared spectrometer 44 lasers 44 strobes 44 spectrophotometer 44 echolocation 44 reticle 44 beeping 44 wavefront 44 Accelerometer 44 multimeter 44 backlit display 44 electron beam 44 ambient light 44 ultraviolet light