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).

Abstract: An afocal zoom refractor telescope 20 is formed by a variable magnification achromatic objective system 18 and a fixed focus eyepiece system 19 aligned on a common optical axis 17 and arranged to provide an internal real image I. The objective system 18 is formed by a primary lens element F and three other lens elements C,D,E, and the eyepiece system 19 is formed by two lens elements A,B. The six lens elements A-F are made of a material which has a useful spectral bandpass in the infrared wavelength region and all refractive surfaces (1-12) intercepting the optical axis 17 are substantially spherical. Objective lens system element E which is proximal the primary lens element F is color corrective with a V-value of not less than 120, negatively powered and with a lower refractive index than the remaining objective lens elements (C,D,F). Element E is fixedly coupled to the adjacent lens element D the pair being mounted for movement in a first locus along optical axis 17.

Abstract: A fire control system for a gun comprises a means 10 for determining the position of a target, computer 14 which receives signals representative of the target position from the means 10 and computes fire control signals according to a known programme, the fire control signals being transmitted to a gun drive mechanism 16. The means 10 includes an optical sighting device 11 containing a visual display 30 on which two images are presented in superimposition. One of the images is of the field of view containing the target while the other image is a pattern of predetermined character which is controllably movable over the visual display by adjustment devices 32A, 32B under control of the operator. The means 10 further includes a ranging device 12 and a manually controllable element 21 for altering the field of view. The arrangement is such that a target is located within the field of view as a result of adjustment of the element 21 for altering the field of view.

Abstract: A waveform generator for generating a plurality of repetitive digital waveforms having a common repetition period which is an integral number of periods of a clock signal, the transitions of each waveform during the repetition period occurring synchronously with pulses of the clock signal comprises a digital storage device E which is preprogrammed with waveform data and with time interval data for each of the waveforms, an address counter D, an interval counter G, a latch F and a clock pulse source Y. The interval counter G is arranged to count to a predetermined count number when it is reset to a value determined by the time interval data present at the output of the storage device E and this sequence is repeated. Shortly after the predetermined count number is achieved the interval counter G supplies an address bit to the storage device E and a count signal to the address counter D so that the device E delivers the pertaining waveform data.

Abstract: A laser photocoagulator 10, comprises a fibre optic guide 13 one end of which is accommodated by an endoscope 14 and the other end of which has a coupling 18 for connection to a laser 11 and a gas supply 12. Launch optics 32 are accurately located in coupling 18 with respect to end 34A of optical fibre 34 which traverses the length of the guide 13 thereby rendering the guide replaceable without dislocation of the endoscope 14, the laser 11 and the gas supply 12. The coupling 18 comprises separate clamp means for the optical fibre 34 and the optics 32 enabling accurate alignment co-axially and spatially so that the laser output is focussed on the free end 34A of the fibre 34 without any requirement to align the laser 11 accurately with optics 32.

Abstract: A signal processing system comprises an analogue shift register of the charge coupled type (24) fed from a sampling device (22) and controlled by a clock arrangement (26) having three independent clocks (26A, 26B and 26C). Clock (26A) determines the sampling rate of sampling device (22) and the rate at which such samples are clocked into register (24). Clock 26C determines the rate at which stored samples are clocked out of the register (24). Clocks 26A and 26C operate in the MHz range. Clock 26B operates in the KHz range and dictates the sample storage interval and clocks the stored samples through a number of storage sites in register (24) during the storage interval to reduce the adverse effects of geometrical and other inhomogeneities of the individual register sites on the individual stored samples.

Abstract: An eyepiece or collimation lens system (22) is formed by three optically-powered lens elements (A, B, C) aligned on a common optical axis (23) and arranged to accept radiation in the infrared wavelength region from a real image (I) and provide a bundle of parallel rays at an exit pupil (.0.), each of the lens elements (A, B, C) is positively powered and made of a material which has a useful spectral bandpass in the infrared wavelength region and the refractive surface (6) of lens element (C) which lies adjacent the real image (I) is flat whereas the other refractive surfaces, (1, 2, 3, 4, 5) of the lens elements (A, B, C) are substantially spherical. A graticule may be mounted on or adjacent the flat refractive surface (6) and each refractive surface may be anti-reflection coated. Conveniently lens element (c) is made of zinc selenide whereas lens elements (A, B) are each made of germanium.

Abstract: An afocal refractor telescope (10) is formed by a fixed focus achromatic objective system (11) and a fixed focus eyepiece system (12) aligned on a common optical axis (13), the objective system (11) being formed by two lens elements (C, D) and the eyepiece system (12) being formed by two lens elements (A, B), each of the four lens elements (A, B, C, D) being made of a material which has a useful spectral bandpass in the infrared wavelength region, and having refractive surfaces (1,2,3,4,5,6,7,8) intercepting the optical axis (13) which are substantially spherical, lens element (c), which is proximal the eyepiece system (12) being color corrective, with a V-value not less than 120, negatively powered and having a lower refractive index than lens element (D) which is positively powered. Conveniently lens element (C) is made of Chalcogenide glass and each of lens elements (A, B and D) is made of germanium.

Abstract: An infrared radiation detecting system comprises a detector element 13A forming part of a detector 13 incorporating a cold shield 14 and an optical system 12, 15, for imaging infrared radiation from a field of view O onto a real image surface 19 spaced from the detector element 13A and relaying the image I from the surface 19 to the detector element 13A is provided with a graticule 20 having markings which are reflective to infrared radiation emitted by the detector 13. Graticule 20 is located at the image surface 19 so that the graticule markings are imaged onto the detector element 13A in superimposition with the infrared radiation from the field of view O.

Abstract: A thermal imager comprises a scanner (13), detector (14) with mount (14A) cooled substantially below ambient temperature, and which via a reflector (16) on the locus (15) along which an image of the detector (14) is effectively scanned provides a characteristic radiation feature to the detector (14) in superimposition with the scanned radiation from the scanner (13). The scanner (13) operates with less than 50% efficiency so that in the detector output signal the scene-derived waveform has a duration T.sub.1 <50%T, where T is the period of the detector output signal. The characteristic radiation feature gives rise to a sync signal at the detector output and is located prior to and closely adjacent the scene-derived waveform at a time interval T.sub.2 prior to the end thereof. This sync signal is detected by a recognition circuit (20) and activates a monostable forming part of a clock circuit (22) for a duration T.sub.3 such that T.sub.2 <T.sub.3 <50%T.

Abstract: An etalon for use in lasers, particularly CW dye lasers, comprises a pair of plates, 10,11 respectively mounted at the ends of a tube 12 with the distal faces 10a, 11a of the plates parallel and the chamber 13 formed within the tube 12 between plates 10,11 is substantially completely filled with a fluid 20 whose refractive index matches that of the plates 10,11 and means 25 are provided for causing extension and contraction of the axial spacing of the plates 10,11. In one embodiment the tube 12 is made of piezoelectric material and the means 25 provides an electrical drive signal to the piezoelectric material. In another embodiment the tube 12 has piezoelectric portions and other portions made of a rigid material. In a further embodiment the tube has portions made of a rigid material which are separated by an elastomer 39 and the means 25 includes a pump 26 which is in fluid communication with the chamber 13.

Abstract: A radiation scanning system comprises a detector 12 which forms part of an assembly 11 maintained at a temperature substantially below ambient, an imaging means 18 for forming an image of radiation from a field of view, a scan member 15 and a relay lens 14 arranged to scan an image of the detector 12 across the radiation image and an arrangement for applying a characteristic radiation feature to the detector 12 at a selected part of the detector image locus 19 lying outside the normal scanned field of the system comprises a mirror 20 arranged to reflect radiation from the cooled assembly 11 onto the detector 12.

Abstract: Apparatus for assessing the thermal sensitivity of optical systems comprises a test target 4 in the form of a plate in which slits 11 are cut at a predetermined spatial frequency. Radiation from a heated bar 1 is reflected from two separate portions thereof on opposite faces A,B of the bar to the test target 4 by concave mirrors 2, 3, radiation from one mirror 3 being reflected by the test target 4 and radiation from the other mirror 2 being transmitted through the slits 11 of test target 4 so that the resulting radiation passes along a common path 9 to a collimator 8 and hence to the optical system under test. The bar 1 may be heated at one end and cooled at the other end such that a temperature gradient is produced along the length of the bar.

Abstract: An optical scanning system comprises a raster scan imager mounted on a support which is rotatable in azimuth, the imager being arranged to provide a line scan which is substantially coplanar with the azimuthal rotational axis and a frame scan which is orthogonal to the line scan, a sensor is provided for monitoring azimuthal rotational rate of the support and a frame scan control means is coupled to the sensor and arranged to provide that the frame scan rate at a field of view is constant and corresponds to a standard T.V. field scan rate irrespective of the azimuthal rotational rate.

Abstract: A laser of the kind in which the lasing medium is a free flowing dye stream incorporates a means of tuning the output wave length of the laser, this means being in the form of a wedged birefringent plate which is driven in a linear mode by a linear translator so that the thickness of the birefringent plate traversed by the intracavity beam of laser light may be varied.

Abstract: A d.c. coupled radiation scanning system having a plurality of radiation detector elements, a multiplexer and a scanned raster display device, including a circuit for compensating for variation in transfer characteristics of the detector elements. The compensating circuit monitors the voltage from each detector element, and derives and measures a voltage function therefrom in synchronism with the multiplexer. The voltage function may be average voltage or the average of the squares of voltages. Additionally, the mean value of all the measured voltage functions is determined over a succession of multiplexer time intervals, each measured value is compared against this mean value and the succession of error signals resulting therefrom is used to modify the signal output from the multiplexer and fed to the video input of the display device.

Abstract: A radiation scanning system comprises a detector, a transfer lens forming a real image of the detector, a rotary scanning means interposed between the transfer lens and the detector image in such a way that as the rotary scanning means is rotated the detector image moves in a circular locus, a concave substantially-spherical mirror concentrically disposed with respect to the detector locus, said locus being at the focal surface of the mirror so that for different rotational positions of the rotary scanning means differently directed parallel bundles of rays emanate from the mirror all intersecting at a pupil, and a second scanning means located at said pupil. The two scanning means provide orthogonal line and frame scans.

Abstract: A method of determining the instantaneous arterial blood pressure of a subject which is a living being without utilizing entry of a needle or the like along an artery is capable of a high degree of accuracy and comprises the steps of applying a pressurizable device in the region of an artery and controllably pressurizing that device with fluid to an extent sufficient to eliminate arterial wall movement without collapse of the artery, the fluid pressure in the pressurizable device being monitored and providing a measure of the instantaneous arterial blood pressure of the subject. A preferred form of pressurizable device is an annular ring or cuff comprising a rigid body of annular shape over the inner surface of which is stretched a latex membrane which is pressurizable with distilled water.