Various embodiments include systems and methods to provide selectable variable gain to signals in measurements using incident radiation. The selectable variable gain may be used to normalize signals modulated in measurements using incident radiation. The selectable variable gain may be attained using a number of different techniques or various combinations of these techniques. These techniques may include modulating a modulator having modulating elements in which at least one modulating element acts on incident radiation differently from another modulating element of the modulator, modulating the use of electronic components in electronic circuitry of a detector, modulating a source of radiation or combinations thereof. Additional apparatus, systems, and methods are disclosed.

Electronic devices may be provided with light sensors. Light sensors may be proximity sensors or ambient light sensors. Proximity sensors may include a light-emitting component and a light-sensitive component. The electronic device may include an enclosure formed from housing structures and some or all of a display for the device. The enclosure may include openings such as openings formed from clusters of smaller openings. Each light sensor may receive light through one of the clusters of openings. The light sensor may receive the light directly through the openings or may receive light that passes through the openings and is guided to the light sensor by light guiding structures. The light guiding structures may include fiber optic structures or light-reflecting structures. Fiber optic structures may fill or partially fill the openings. Light reflecting structures may be machined cavities in an internal support structure.

A device for measuring caustic parameters of a laser beam includes a beam splitter for splitting the laser beam into at least three spatially separated partial beams, and a detection unit for detecting images of the partial beams. A beam path from an input of the device to the beam splitter defines a beam axis for the laser beam, along which the laser beam propagates until entering the beam splitter. The beam splitter includes an optical lens, and a partially reflective surface configured to split the laser beam into the at least three partial beams by partial reflection within the optical lens. The optical lens is positioned off-axis such that an optical axis of the optical lens extends off-axis to the beam axis, and/or the optical lens is tilted such that the optical axis of the optical lens forms an angle with the beam axis that deviates from 0.