Security documents often incorporate optically variable devices to prevent or hinder counterfeiters. Disclosed herein are layered optically variable devices such as color-shift foils, and methods for their production and use. Such devices afford new techniques for a user of a security document to check quickly and easily whether the security document is a legitimate document or a counterfeit copy.

A tunable laser has a solid state laser medium having an optical gain region and generates coherent radiation through a facet. A lens collects the coherent radiation and generates a collimated light beam. Components of an external cavity include a reflective surface and an optical filter, the reflective surface reflecting the collimated beam back to the lens and the laser medium, the optical filter positioned between the reflective surface and the lens and having two surfaces with a thermally tunable optical transmission band within the optical gain region of the laser medium. The optical filter (1) transmits a predominant portion of the collimated beam at a desired wavelength of operation, and (2) specularly reflects a remaining portion of the collimated beam from each surface, the collimated beam being incident on the optical filter such that the reflected collimated beams propagate at a non-zero angle with respect to the incident collimated beam.

Embodiments include 3D display devices and methods of operation. In an example device, a light-emitting layer is provided with an addressable array of light-emitting elements. An optical layer overlays the light-emitting layer. The optical layer includes an array of lenses operative to substantially collimate light from the light-emitting layer. To suppress stay light, an angular filter layer is provided along an optical path from the light-emitting layer to an exterior of the display. The angular filter is operative to substantially block light having an incident angle greater than a threshold angle and to substantially transmit light having an incident angle less than a threshold angle. The angular filter may be a thin-film interference bandpass filter. Different regions of the angular filter may be tuned for different wavelengths of light.

According to an example, a first mirror layer may be formed on a substrate. A first set of spacer layers may be deposited on the first mirror layer to be positioned above a first group of the sensing elements and a second set of spacer layers may be deposited on the first mirror layer to be positioned above a second group of the sensing elements, in which the second set of spacer layers differs from the first set. In addition, a second mirror layer may be formed above the deposited first set of spacer layers and the deposited second set of spacer layers.

In illustrative implementations, an imaging system may comprise a lens, an optical cavity and a time-of-flight camera. The imaging system may capture an image of a scene. The image may be formed by light that is from the scene and that passes through the optical cavity and the lens. In some cases, the lens is in front of the optical cavity, enabling the Euclidean distance between the lens and the camera sensor to be less than the nominal focal length of the lens. In some cases, the lens is inside the optical cavity, enabling the camera to acquire ultrafast multi-zoom images without moving or changing the shape of any optical element. In some cases, the lens is behind the optical cavity, enabling the system to perform ultrafast multi-spectral imaging. In other cases, an optical cavity between the scene and time-of-camera enables ultrafast ellipsometry measurements or ultrafast spatial frequency filtering.

A laser protection eyewear lens includes a lens substrate comprising an embedded wavelength filter having a first filter function, and a multi-layer dielectric filter applied to at least one of an inside and an outside surface of the lens substrate that comprises a second filter function having at least one center wavelength and bandwidth. The first filter function of the embedded wavelength filter and the second filter function of the multilayer dielectric filter produce a combined filter function that attenuates light reflecting off the multi-layer dielectric filter.

Optical filter assemblies based on either a parallel plate optical assembly or a polarization separation optical assembly are described. The optical assemblies usefully separate randomly polarized light with at least two transmission wavelengths from an optical communication signal.

An arrangement for hyperspectral imaging, comprising an imaging sensor (170,270); a band-pass filter element (130,230): at least one imaging optics element (120,160,220,260) configured to form an image on the imaging sensor (170,270); and a first adjustable multi passband filter (150a,255); wherein the first (150a,255) adjustable multi passband filter is configured to be adjusted by tilting.

According to one aspect, the invention relates to an angular optical filtering element (E.sub.i) optimized for angular filtering about a given operating angle of incidence (θ.sub.i, 1) in a given spectral band. The angular filtering element (E.sub.i) comprises a first nanostructured, band-pass, spectral filter (11.sub.i, 301) and a second nanostructured, band-pass, spectral filter (12.sub.i, 302). Each of the first and second spectral filters comprises, respectively, in said spectral band, a first and a second central filtering wavelength that respectively has a first and second angular dispersion curve defined depending on the angle of incidence (θ.sub.inc) on the optical filtering element (E.sub.i), the curves of angular dispersion being secant about the operating angle of incidence (θ.sub.i, 1) of the optical filtering element. The invention applies to the production of a selective angular filtering device and to a multidirectional optical detection system.

A display substrate, a manufacture method thereof and a transparent display device are provided. The display substrate includes a substrate (1); a plurality of pixel regions, each including a plurality of sub-pixel regions; and a first metallic layer (3), a passivation layer (5) and a second metallic layer (4) that are formed on the substrate in sequence and are located at the sub-pixel regions. The first metallic layer (3) and the second metallic layer (4) both are transflective metallic layer, and different parts of the passivation layer located at the plurality of sub-pixel regions of a same pixel region have different thicknesses. The first metallic layer (3), the passivation layer (5) and the second metallic layer (4) constitute a Fabry-Perot cavity which allows light having different wavelengths to transmit there-through depending on different thicknesses of different parts of the passivation layer.