Dr. Crusher uses an IP scanner to detect an interphasic organism
An interphasic scanner, or simply IP scanner, was a sensor device used aboard Starfleet vessels in the 24th century, for use in detecting objects which existed in a state outside normal visual and sensor acuity.
In 2370, Doctor Beverly Crusher used a handheld IP scanner to reveal an infestation of interphasic organisms aboard the USS Enterprise-D. Later, Lieutenant Worf used an IP scanner to inspect the area around the Enterprise in an attempt to find more evidence of the organisms. (TNG: "Phantasms")
The same prop later appeared as an engineering tool in the episodes "The Next Phase", "Eye of the Beholder", and "Bloodlines".