Abstract: Optical components (16), particularly germanium components, are provided with a coating on exposed surface (15) within a vacuum chamber (17) by production of a glow discharge plasma containing carbon and another depositable element from feedstock gases which are fed to the chamber (17) via mass-glow rate controllers (9, 10, 11). The mass flow rate of the feedstock gases is maintained substantially constant at predetermined levels during respective time intervals to provide a multilayer coating of predetermined characteristics. Typically the coating has at least one first layer which is amorphous hydrogenated germanium carbide, at least one second layer which is amorphous hydrogenated germanium and at least one third layer which is amorphous hydrogenated carbon, these layers being ordered such that each second layer is bounded on each side by a first layer and the third layer is bounded on one side by a first layer, the other side of the third layer forming the exposed surface of the coating.

Abstract: A forward looking infrared optical system comprises a refractor telescope 20 in combination with a powered window and fold mirror arrangement 30. Arrangement 30 comprises a powered window element J with concentric spherical refractive surfaces having their common center of curvature on the common optical axis 19 where the latter is folded by the reflective surface 27 of the mirror element I. Because the window element J is powered it introduces significant spherical aberration and some color aberration to the system however telescope 20 provides compensation for such aberrations by being non-afocal and non-diffraction limited. This is achieved by the objective system 21 of the telescope 20 being telephoto and formed of two elements H,G of which H is positively powered and G is negatively powered and color corrective. The refractive surfaces of element G are each spherical whereas at least one refractive surface (15) of element H is aspheric.

Abstract: A multiple wavelength operating laser (10) having a pump cavity or enclosure (14) surrounded by an optical pumping arrangement (17) comprises a plurality of substantially concentric tubes (21A, 21B) each having windows for emission of radiation and enclosing respective bodies of liquid lasing media. The lasing media may be flowed through the respective tubes and are preferentially arranged so that the fluorescence spectra of the lasing medium in one tube overlaps the absorption spectra of the lasing medium in the adjoining tube so that the one lasing medium optically pumps the other lasing medium in addition to optical pumping from the optical pumping arrangement (17).

Abstract: An infrared afocal refractor telescope (40) comprises a zoom system (27), a collecting system (28) and an eyepiece system (30) arranged in a common optical axis (26). The zoom system (27) is formed by a fixed objective lens component (K) and by a first lens component (H) mounted on a carriage (32) and by a second lens component (I,J) mounted on a carriage (31), the carriages (32,31) being separately movable along the optical axis (26). The movable lens components of the zoom system (27) each have the same sign of optical power and the variation in telescope magnification provided by selective positioning of the carriages (32,31) is at least 5:1 in range. The locus (34,33) of movement of each of the two movable lens components (H;I,J) renders the telescope athermalized.

Abstract: An infrared objective lens assembly comprises a four-component zoom system (25) which accepts from object space (22) radiation in the infrared waveband, and a one-component collecting system (26) which forms a real image (24) of that radiation. The components of the zoom (25) and collecting (26) systems are formed by lens elements (D,E,F,G,H,I) such that with respect to the collecting system (26) the first (E) and third (H,G) components of the zoom system (25) are mounted on a common carriage (41) and are selectively positionable along the optical axis (21) whereas the second (F) and fourth (I) components of the zoom system (25) are fixedly positioned on the optical axis (21) whereby the zoom system (25) is optically-compensated and of variable effective focal length. The fourth (I) zoom system component is formed by a lens element having an aspheric refractive surface (17) but the refractive surfaces (9-16) of all other lens elements (E,F,GH) of the zoom system (25) are non-aspheric.

Abstract: An imaging system (10) comprises an imaging data-collection station (11) having a camera (15) with a field of view (16) mounted on platform (13) rotatable about azimuthal axis (14). Collected image data is delivered on line (20) to a monitoring station (12) together with data on line (19) representative of the angular position of platform (13) which is sensed by sensor (18). The monitoring station (12) incorporates at least one channel each channel having a display device (25) having a known display field (30, .alpha..sub.1), an operator-actuable sensor (26) which selects a particular angular position (.theta..sub.1), within the wide angle field (17) traversed by fixed field of view (16), a gate device (28) for capturing the pertaining image data from line (20) and a store (29) for storing captured data.

Abstract: A radiation scan system (10) incorporates a scanning device (13) which transfers radiation between transmitting station (12) and receiving station (11) with simultaneous mapping of a point (14) in station (11) into a line (15) in station (12). Station (12) is in the form of a distant plane. Scanning device (13) has at least one mirror (16) mounted on a carrier (17) movable about an axis (18) which lies in the plane of the angular offset between the radiation beams at scan device (13) incoming from and outgoing to the stations (11,12). A refractive prism corrector (26) is located in the path of the radiation beam between scan device (13) and station (12) whereat line (15) exists, the vertex edge (27) of the prism corrector (26) being perpendicular to axis (18) and the parameter values of the prism corrector (26) are such that at least the line (15) in station ( 12) is straight.

Abstract: Apparatus (10) for identifying the position of a body (21) in a scene (20) comprises a first station (11) incorporating a raster-scan imaging device (15) having a field of view (19) with azimuthal and elevational rotational freedom and variable magnification the settings of which are respectively sensed by sensors (24,25,26). A signal processor (16) collects the video signal from device (15) and the sensor signals and adds the latter to part of the raster scan which, in playback, does not obscure the video picture generated by the video signal. The processor (16) is connected by lead (28) to a second station (12) which incorporates a raster-scan playback device (32) associated with an operator-actuated electronic cursor generator (33).

Abstract: An infrared radiation detecting system comprises an optical imaging system (25) for receiving radiation from a field of view (23) and delivering that radiation to an image surface (16). A background limited detector unit (26) having a detecting surface (.phi.) located in a cold shield housing having a cooled aperture (13) is spaced from image surface (16) and a transfer lens system (24) is interposed to transfer infrared radiation therebetween. Lens system (24) is arranged to focus the radiation at the detecting surface (.phi.) of the detector unit (26) such that the focussed radiation field curvature coincides with the physical curvature of detecting surface (.phi.), to form a pupil which is coincident in space with the position of the cooled aperture (13) and to dimension the pupil to match the dimension of the cooled aperture (13). To achieve these effects the transfer lens system (24) is formed by four lens elements (A,B,C,D) of selected power, axial spacing, and refractive surface curvature.

Abstract: An optical slip ring comprises a housing made of low refractive index material which defines a hollow toroid (10) and a pair of passageways (15A, 15B) leading from the toroid (10). One passageway (15B) leaves the toroid (10) steplessly in a clockwise direction and passageway (15A) leaves the toroid (10) steplessly in an anti (counter-)clockwise direction. The toroid (10) and the passageways (15A, 15B) are filled with high refractive index fluid. The housing is formed in two portions which are mounted for relative rotation about an axis (13) perpendicular to the toroidal equatorial plane (12) and coincident with the center (14) of the toroid, each portion having an interface lying on a surface of revolution (which may be the toroidal equatorial plane (12) ) generated about the axis (13), one housing portion incorporating one passageway (15A) and the other housing portion incorporating the other passageway (15B).

Abstract: An infrared objective lens system (15) comprises a primary lens group (13) air spaced from a secondary lens group (14) by means of a support assembly (16). The primary lens group (13) and secondary lens group (14) are aligned on a common optical axis (10) and are arranged to form a real image (9) at an external image surface from infrared radiation entering the system (15) through a pupil .0. in object space (11). Primary lens group (13) is self-compensated for chromatic aberrations, is positively powered and is made of material the refractive index of which is relatively temperature insensitive such as arsenic triselenide and/or zinc selenide. The secondary lens group (14) is positively powered, introduces minimal chromatic aberrations and is formed by a positively powered lens (C) and a negatively powered lens (D). Lens (C) is made of material the refractive index of which is relatively temperature insensitive such as arsenic triselenide.

Abstract: A telescope objective system (10) is formed by a primary lens having a single lens element (A) aligned on a common optical axis (11) with a secondary lens having two lens elements (B,C) the shape and power distribution of lens elements (A,B,C) being such as to compensate for monochromatic aberration of the system, each lens element (A,B,C) being made of a material which has a useful spectral bandpass in the infrared wavelength region and lens elements (B,C) having refractive surfaces (16, 15, 14, 13) intercepting the optical axis (11) which are substantially spherical, the system having a planar image surface (11) and an effective focal length greater than the axial distance between the image surface (11) and the distal refractive surface (18) formed by the primary lens element (A). Primary lens element (A) is positively powered and made of germanium and at least one of the secondary lens elements (B,C) is made of a Chalcogenidae glass such that the system (10) is achromatic in the infrared wavelength region.

Abstract: A gun fire control system comprises a computer (15) having a first memory (15A) preprogrammed with true range to standard ballistic range conversion data and is operable on receipt of a true range value from a rangefinder (16) to output the corresponding standard ballistic range value. A second memory (15B) of the computer (15) is preprogrammed with correction coefficients (A,B,M,N) arranged in sets pertaining to different types of ammunition one set being operable according to the position of a selector switch (13) and being delivered to a calculator (15C) together with an operator correction value (COR) (from buttons 14A, 14B) which is a judgment on the magnitude and direction by which a projectile misses a target sighted according to the range value presented at display (11). Calculator (15C) operates according to a predetermined algorithm to establish parameter correction changes (.DELTA.AD, .DELTA.CT) and delivers these changes to calculator/store (15D) which updates and stores parameter values (AD, CT).

Abstract: An afocal telescope (20) comprises an objective system (21) and an eyepiece system (23) aligned on a common optical axis (19), the objective system (21) forming a real image (24) of radiation received from object space (17) and eyepiece system (23) being arranged to provide a magnified view of the object space scene at a pupil .phi. in image space (18). The eyepiece system (23) is formed by a triplet of lens elements A,B,C of which A and B are positively powered and C is negatively powered. Element C has a concave refractive surface (6) adjacent image (24) and a convex refractive surface (5) which is separated from the adjoining refractive surface (4) of element B by an air space which, in the axial direction, is substantially zero on the axis (19) and which progressively increases in magnitude as the distance off axis increases.

Abstract: An afocal refractor telescope is formed by a fixed focus achromatic telephoto objective system (10) and a fixed focus eyepiece system (11) aligned on a common optical axis (12) and is arranged to provide an internal real image (13). The objective system (10) is formed by a primary lens element (D) and a secondary lens element (C) and the eyepiece system (11) has at least two lens elements (A, B). Each of the lens elements (A,B,C,D) of the telescope is made of a material having a useful spectral bandpass in the infrared wavelength region and has refractive surfaces (1,2,3,4,5,6,7,8) intercepting the optical axis (12), at least one of the refractive surfaces (7,8) of the primary objective lens element (D) being aspheric whereas the refractive surfaces (1,2,3,4,5,6) of the lens elements (A,B,C) are substantially spherical. The aspheric surface (7,8) possesses only a small degree of asphericity and is defined by an equation in which the third and higher order aspheric coefficients are zero.

Abstract: An afocal dual magnification refractor telescope is formed by a fixed focus achromatic telephoto objective system (21) formed by a primary objective lens element (H) and a secondary objective lens element (G) aligned on a common optical axis (19) with a fixed focus collimation system (22) and interchangeable high and low magnification lens systems (23,24) each of which is arranged to provide an internal real image (25,26). The high magnification lens system (23) is formed by two lens elements (B,C) and the low magnification lens system (24) is formed by three lens elements (D,E,F). The eight lens elements (A,B,C,D,E,F,G and H) are made of materials which have a useful spectral bandpass in the infrared wavelength region and the refractive surfaces of these lens elements which intercept the optical axis (19) are substantially spherical except for one or both refractive surfaces (15,16) of the primary objective lens element (H).

Abstract: A laser rangefinder comprises a transmitter (19) controlled by sequence-controlled pulses emitted by a timer (16) following actuation of a switch (17) by an operator. The receiver of the rangefinder comprises an avalanche photodiode (APD) (10) the sensitivity of which is controlled in a time-programmed manner by a bias voltage controller (11) which receives timing pulses from the timer (16). The time-programmed control operates to render the APD 10 insensitive to protect the receiver against optical element backscatter and atmospheric backscatter prior to rendering the APD 10 sensitive to monitor return pulses from remote targets.

Abstract: An optical scanning system comprises a rotor assembly (10) rotatable about axis (11) and having a first reflective zone (12) composed of planar facets (12A, 12B, 12C, etc.) and a second reflective zone (13) composed of facets (13A, 13B, 13C etc.) which may be planar or curved. An array of radiation detectors (26) is focussed by static focussing means (14) at a first reflection station through which the facets of the first zone (12) sequentially pass. Further static optical means (15) are provided to direct radiation between the first reflection station and a second reflection station through which the facets of the second zone (13) sequentially pass. The facets (12A, 12B, 12C etc.) of the first reflective zone (12) each have a normal disposed at an angle .psi. to the rotational axis (11); the incident and reflected radiation beams at the first reflection station each have a half cone angle .alpha.

Abstract: A process for coating the surface of a material with a carbonaceous coating by vacuum deposition derives the carbon in substantially pure form from a hydrocarbon gas plasma, the surface to be coated being coupled to an A.C. power source operating at a frequency below 500 kHz at which the electrical impedance of the plasma is substantially non-varying during the deposition process. Because the plasma impedance is substantially constant the process is safe and reproducible and can be carried out without dynamic monitoring and adjustment procedures and there is no requirement for an impedance matching network between the A.C. power supply and the vacuum chamber. Frequencies in the range 300-400 kHz with applied voltages of the order of 1KV or greater have been found to give good results.

Abstract: In a system (10) comprising a trunnion-mounted aiming device (11) and a trunnion-mounted sighting device (14) interconnected by a tracking link (13) and having an associated visual display (16) providing an image of the field of view containing the sight line (15) of the sighting device (14) there is provided a means of accurately positioning an aiming mark designating the pointing direction (12) of the aimed device (11) in the visual display (16). This positioning arrangement is provided by an elevation sensor (18) associated with the aimed device (11), an elevation sensor (19) associated with the sighting device (14), an electronic indicator mark generator (28) and an electronic processor (20), the latter being operable according to the measurements from the sensors (18,19) to deflect the mark generated by the generator (28) so as to compensate in the elevation axis for backlash and inertia of the link (13) and in the traverse axis for lack of parallelism of the trunnion mountings of the devices (11,14).