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: 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 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 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: 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 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.