An apparatus includes an optical emitter configured to emit a first optical signal along an optical path towards a target object in an outdoor environment. The apparatus includes an optical detector positioned collinearly with respect to the optical emitter. The optical detector is configured to detect a second optical signal that is retro-reflected from the target object. The apparatus includes a lock-in amplifier coupled to the optical detector. The lock-in amplifier is configured to generate, based on the first optical signal and the second optical signal, a signal indicative of a retro-reflectivity of the target object in the outdoor environment.

Systems and methods for determining the cleanliness of a surface. Surface marking systems of the present disclosure can include a plurality of retroreflective microspheres dispersed in or dispensed on a carrier. Applicators of the present disclosure can include a container comprising the surface marking system, and a dispenser. Methods of the present disclosure can include applying the surface marking system to at least one discrete site on the surface; illuminating the at least one discrete site on the surface with visible light, after a cleaning; and detecting retroreflection emitted from the at least one discrete site on the surface in response to illuminating the at least one discrete site to determine the effectiveness of the cleaning of the surface.

A multipass cell (300) comprising: a first reflector arrangement (305A, 305B); and a second reflector arrangement (307), the first (305A, 305B) and second (307) reflector arrangements defining an optical cavity (315) therebetween and the cell; wherein the first reflector arrangement (305A, 305B) is configured such that light incident on the first reflector arrangement (305A, 305B) is at least partially retroreflected towards the second reflector arrangement (307), wherein the second reflector (307) arrangement comprises a concave surface that is reflective, wherein at least one of the first (305A, 305B) and second (307) reflector arrangements comprises an aperture (306) for allowing light to enter and/or exit the optical cavity (315).

A device is presented. The device includes an electromagnetic guiding device to provide electromagnetic radiation, a reflector that reflects a portion of the electromagnetic radiation to generate a reflected portion of the electromagnetic radiation, wherein the reflector is fully immersed in a multiphase fluid, and a processing subsystem that analyzes the multiphase fluid based upon at least a portion of the reflected portion of the electromagnetic radiation, wherein a principal optical axis of the electromagnetic guiding device substantially aligns with a principal optical axis of the reflector.

Apparatuses and methods for monitoring curing of photocurable material are disclosed. The methods generally include directing an ultraviolet cure light into a photocurable material, wherein the ultraviolet cure light causes the photocurable material to cure; directing a probe light into the photocurable material through an optical fiber during the cure; collecting a back reflection signal from the photocurable material with the optical fiber; and determining a refractive index change of the photocurable material during the cure.

A method is provided for detecting a roadway of a vehicle including at least the following steps: generating a light signal and emitting the light signal onto a lit area of the roadway, receiving retroreflected radiation of the lit area and generating an image signal, evaluating the image signal. For this purpose, it is provided that the light signal having light structures is generated, the image signal is evaluated as a two-dimensional light pattern, a detection of pattern characteristics corresponding to the light structures being carried out in the light pattern during the evaluation of the image signals, a signal strength of the image pattern being evaluated in a space-resolved manner and a reflecting behavior of the lit area being inferred therefrom, and a roadway surface being inferred from the reflecting behavior.

A gadget for retroreflected signal measurement is disclosed. The gadget for measuring the retroreflected signal includes a partitioning wall; a portable terminal receiving portion disposed on one surface of the partitioning wall; a biosensor receiving portion disposed on the other surface of the partitioning wall and constructed to receive a biosensor therein; a light exit channel defined in the partitioning wall and at one side thereof; and a light-receiving channel adjacent to the light exit channel and defined in the partitioning wall, wherein light passes through the light exit channel and then is reflected from the biosensor, and then is incident into the light-receiving channel.

An apparatus includes an optical emitter configured to emit a first optical signal along an optical path towards a target object in an outdoor environment, and an optical detector positioned collinearly to the optical emitter with respect to an optical axis corresponding to the optical emitter. The optical detector is configured to detect a second optical signal that is retro-reflected from the target object.