An optical probe for a bio-sensor selectively conjugated to a target analyte and configured to retro-reflect incident light thereto is disclosed. The optical probe for the bio-sensor includes: a transparent core particle; a total-reflection inducing layer covering a portion of a surface of the core particle, the inducing layer is made of a material having a refractive index lower than a refractive index of the core; a modifying layer formed on the total-reflection inducing layer; and an analyte-sensing substance bound to the modifying layer, the sensing substance is selectively conjugated to the target analyte. This optical probe may serve as an excellent optical probe for both a non-spectral light source and a spectral light source.

A hand-held test device and a method for testing an object having at least one retrore-flective region and at least one fluorescent region, e.g. an item of high-visibility clothing. The hand-held test device includes a white light LED, a UV LED, a connnon photoreceiver, and a control unit. In a reflection test mode, a reflective region is briefly irradiated with white light and reflects onto the photoreceiver. In at least one fluorescence test mode, ultraviolet light is emitted by the onto a fluorescent region, which generates fluorescent light of a corresponding colour via the fluorescence, which is received by the photoreceiver. In all test modes, a receive sig corresponding with the irradiation strength is generated at the photoreceiver and transmitted to the control unit for evaluation, e.g. for carrying out a threshold value comparison with a predefined threshold value for the receive signal. Every test mode can preferably have a separate predefined threshold value for this purpose.

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).

An apparatus for measuring retro-reflectivity of a target object in an outdoor environment includes a modulator to modulate a first optical signal based on a specified modulation value, an optical emitter, coupled to the modulator, to emit the first optical signal along an optical path towards the target object, and an optical detector positioned collinearly with respect to the optical emitter. The optical detector detects a second optical signal that is retro-reflected from the target object. The apparatus includes a lock-in amplifier coupled to the modulator and the optical detector. The lock-in amplifier receives a first electrical signal from the modulator and a second electrical signal from the optical detector, and generates, based on the first electrical signal and the second electrical signal, a third electrical signal indicative of the retro-reflectivity of the target object.

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.

The method of the invention comprises: obtaining a sequence of at least two images, with different levels of illumination; extracting the region containing the sign in the image; calculating the luminance values of the signs; and obtaining the difference in luminance of the sign corresponding to the two levels of illumination. The value obtained is the luminance of the sign (11) corresponding to an illumination equal to the difference between the illuminations, or additional illumination. This result is based on the additive property of luminance, according to which the luminance of a sign is the sum of the luminance produced by each source of illumination. A basic illumination device (5), an additional illumination device (7), at least one camera for taking images, and image recording, positioning and synchronism systems are required to implement the method.

This invention relates to an apparatus for retro-reflection measurement. By using the one or more sampling devices each consists of a holed mirror and an circular aperture, and corresponding one or more measuring devices, it realize the retro-reflection measurement in one or more observation angles at one time. By flexibly selecting the size of the circular apertures and holed mirrors, it can accurately adjust the measuring annular bands and corresponding observation angles. Without any other intermediate devices, it can realize complete annular band of light measurement which ensures the measurement accuracy. At the same time, filters and monitor device can be set flexibly to realize various measurement functions. It has the advantages of speed measurement, high accuracy, small volume, wide application, comprehensive functions, and can be widely applied in laboratory, industrial production line and field measurement etc.

An apparatus for measuring retro-reflectivity of a target object in an outdoor environment includes a modulator to modulate a first optical signal based on a specified modulation value, an optical emitter, coupled to the modulator, to emit the first optical signal along an optical path towards the target object, and an optical detector positioned collinearly with respect to the optical emitter. The optical detector detects a second optical signal that is retro-reflected from the target object. The apparatus includes a lock-in amplifier coupled to the modulator and the optical detector. The lock-in amplifier receives a first electrical signal from the modulator and a second electrical signal from the optical detector, and generates, based on the first electrical signal and the second electrical signal, a third electrical signal indicative of the retro-reflectivity of the target object.

A retroreflectometer for non-contact measurements of optical characteristics of retroreflective materials from a range of distances includes a light source for emitting a light beam; a first moving mirror assembly for scanning the light beam; a collimating lens for collimating the scanning light on an illumination spot on the surface of the DUT; an imaging lens for receiving a reflected scanning light comprised of the collimated scanning light reflected from the surface of the DUT; a second moving mirror assembly for controlling a predetermined observation angle, wherein the first moving mirror assembly and the second moving mirror assembly moved in synchronization to maintain concentricity of the illumination spot on the surface of the DUT; a light collector for collecting the reflected light from the second moving mirror assembly; a processor including a memory for determining the optical characteristics of the surface of the DUT responsive to the collected reflected light.

A retroreflectometer for non-contact measurements of optical characteristics of retroreflective materials from a range of distances includes a light source for emitting a light beam; a first moving mirror assembly for scanning the light beam; a collimating lens for collimating the scanning light on an illumination spot on the surface of the DUT; an imaging lens for receiving a reflected scanning light comprised of the collimated scanning light reflected from the surface of the DUT; a second moving mirror assembly for controlling a predetermined observation angle, wherein the first moving mirror assembly and the second moving mirror assembly moved in synchronization to maintain concentricity of the illumination spot on the surface of the DUT; a light collector for collecting the reflected light from the second moving mirror assembly; a processor including a memory for determining the optical characteristics of the surface of the DUT responsive to the collected reflected light.