The Secretary of State for Defence in Her Britannic Majesty's Government

Qinetiq Limited

The Secretary of State for Defence in Her Brittanic Majesty's Government

Philip Sutton

Herbert A French

Andrew P Shaw

William Dawber

Peter F Hirst

Brian Condon

Ewan D Findlay

Arthur Maitland, Deceased

A filter for removing coherent radiation from a source in a field of view, substantially independent of the size of the source, comprises a first reticlelocated in the path of received light, a first lensproducing an optical transform of the first reticleat a second reticlelocated in the image plane of the first lens, a second lensproducing an optical transform of the second reticleand a third reticlelocated in the image plane of the second lens. The arrangement is such that the spatial transmittance of the third reticleis selected to block at least part of the diffracted image of the first reticleproduced in the image plane of the second lensand characteristic of the coherent radiation. Preferably the optical transforms are Fourier Transforms. A monochromatic coherent source in the field of view produces a pattern of diffracted energy in the image plane of the second lens which is independent of the size of the source. Thus, by providing a suitable reticlein the image plane of the second lens light from a coherent source in the field of view can be blocked while polychromatic light is transmitted. The first and second reticles may be periodic picket-fence reticles or different spatial frequencies may be used for the first and third reticles so as to vary the stop-band characteristics of the filter.

Spectral filter

An electro-optical detection system for detecting objects embedded in a partially transmitting medium. The system includes a receiver for receiving electromagnetic radiation and a device for separating the received radiation into two separate spectral channels. A detector in each of the spectral channels for providing a signal indicative of the received radiation in each spectral channel. A signal processor, responsive to the outputs of the detectors, having a signal channel where transmission of light of the signal channel wavelength in the medium is high and having a reference channel where attenuation of light of the reference channel wavelength in the medium is high. The signal processor ensures that the reflected light at both signal and reference wavelengths are of similar intensity and geometric distribution. A subtractor provides a difference output in which the signal and reference channels are subtracted, removing the effect of reflected light.

Electro-optical detection system

Method for manufacturing optical components with periodic or

Electro-optical detection system for reflection free underwater images

Optical multiplexer

A wavelength-independent-interferometer comprises means to receive light (10) from a field of view, means (BS1) to separate the light into two beams (11, 12), means (BS2) to combine the two beams, and dispersive means (30) interposed in the path (12) of one of the two beams to produce a wavelength-dependent shear. The dispersive means may be a transmission diffraction grating or a reflection grating. In the arrangement shown the optical elements are combined in a modified Mach-Zehnder interferometer. When the conventional Mach-Zehnder interferometer is illuminated with coherent light the separation of interference fringes produced in the interference plane is inversely proportional to the wavelength. By introducing a dispersive element in the invention the detector is sensitized to a pre-determined fringe separation. A moveable reticle is placed in front of a detector to sensitize the detector to the fringe pattern.

Wavelength-independent interferometer for optical signal processing

An interference device for discriminating between radiation sources of differing coherence length comprises means to divide received radiation from a source into two components. A path difference, defining a coherence length cut-off, is introduced into the path of one component and the components are brought together for interference. The recombined light passes through a reticle with alternate opaque and tranparent bars and an optical band-pass filter to a detector. Interference fringes present in the plane of the reticle are swept across the reticle by the action of the collection optical system of the device which includes a scanning rotating mirror. Two similar devices can be arranged for band-pass coherence length filtering and when used in conjunction with a light soruce whose coherence is modulated the device can be used for signalling.

Radiation interference devices

Growing community of inventors

Hampshire, United Kingdom

Philip Sutton