One or more electromagnetic radiation sources, such as a light emitting diode, may emit electromagnetic waves into a volume of space. When an object enters the volume of space, the electromagnetic waves may reflect off the object and strike one or more position sensitive detectors after passing through an imaging optical system such as glass, plastic lens, or a pinhole located at known distances from the sources. Mixed signal electronics may process detected signals at the position sensitive detectors to calculate position information as well as total reflected light intensity, which may be used in medical and other applications. A transparent barrier may separate the sources and detectors from the objects entering the volume of space and reflecting emitted waves. Methods and devices are provided.