GB1605014A - Range responsive apparatus - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO RANGE RESPONSIVE APPARATUS (71) We, ELLIOTT BROTHERS (LONDON) LIMITED, a British Company of Marconi House, New Street, Chelmsford, Essex, CMI 1PL, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to range responsive apparatus and in particular to range responsive apparatus in accordance with the invention in co-pending application No. 7557/74 (Serial No. 1605012) and 23173/74 (Serial No. 1605012) (Cognate) or our Associate, The Marconi Company Limited.

According to the invention in the above mentioned application a range responsive apparatus comprises energy sensitive means arranged to receive electro-magnetic energy simultaneously from different spaced portions of a field of view and means for rotating said field of view about an axis of rotation to cause said field of view to sweep across a target and wherein if the bound- aries of said different portions of said field of view converge said axis of rotation is located on the target side of the region at which said boundaries converge whereby, in operation, the electrical output of said energy sensitive means includes a component whose frequency is dependent upon the range of said target.

Preferably in accordance with the invention in the above mentioned application said energy sensitive means comprises one energy sensitive detector arranged to receive energy from all of said spaced portions of said field of view.

Since in the output of said energy sensitive means a frequency component will appear which depends upon the range of a target the apparatus may be used to form a range measuring apparatus in which case frequency responsive means are provided for indicating the range of a target. Since targets at different ranges will result in the generation of different frequency components at the output of said energy sensitive means, one or more frequency and selective filters may be connected to the output of said energy sensitive means to provide one or more range windows so that selected ranges are excluded. This feature may be utilised to exclude unwanted responses from objects which come within the field of view but which are not of interest.The output of any filter may be applied to frequency responsive means for indicating the range of a target within the corresponding range window or windows. In addition or alternatively the output of any filter may be applied to a frequency responsive means which generates a signal indicating the presence of a target at a range of interest within the range window or windows.

Normally said energy sensitive means is infra-red energy sensitive means.

Said boundaries of said different portions of said field of view may be parallel but preferably said boundaries of said different portions of the field of view are arranged to be divergent in the direction of a target.

A series of individual reflective elements, one for each portion of the field of view, may be introduced beyond (with respect to a target) the axis of rotation, each elemental reflective element being arranged to direct electro-magnetic energy via a different slit in a grating on to a common detector. In effect, in this case the portions of the field of view are provided by the grating imaged in space by said elemental reflective elements.

Normally the slits are narrow in the plane of rotation and relatively long in a plane at right angles thereto in order to provide good energy gathering properties.

In one embodiment of the invention in the above mentioned application, said elemental reflective elements are so inclined that the images of the slits in the grating are closed-up in the field of view so that the field of view is divided into a series of adjacent parts each an image of a different slit and means are provided for optically dividing each slit, and hence each of said adjacent parts of the field of view, into two portions along its extension in a direction at right angles to the plane of rotation, energy received by one portion of each slit being directed on to one detector, whilst energy received on the other portion of each slit is directed on to another detector, the outputs of which are arranged to be combined in anti-phase prior to being applied for connection to frequency measunng means.The embodiment described above operates very satisfactorily, particularly at longer ranges.

However, because each reflective element handles two portions of the field of view a certain amount of confusion may be experienced at short ranges between the two portions of the field of view handled by each reflective element, due to the common imaging area and according to a modification a series of individual reflective elements are provided, one for each portion of the field of view, the individual reflective element for one portion of the field of view being arranged to direct light into one portion of one slit in the grating, whilst an adjacent individual reflective element is arranged to direct light received from the adjacent portion of the field of view through the other portion of the same slit.In other words, for each adjacent part of the field of view formed by an image of a slit, two individual reflective elements are provided each associated with a different portion of the same slit.

In another embodiment of the invention in the above mentioned application focusing electro-magnetic energy reflective elements are provided each arranged to image an electro-magnetic energy detector into space, each focusing reflective element viewing a different spaced portion of the field of view.

Preferably, a second electro-magnetic energy detector is provided which is arranged to be imaged into space by a second array of focusing electro-magnetic energy reflective elements, the focusing reflective elements of said second array being interspersed in alternating fashion between the focusing reflective elements of said first array and arranged to view different spaced portions of the field of view which are interspersed in alternating fashion with the portions of the field of view viewed by the focusing reflective elements of said first array. Normally the portions of the field of view viewed by all of the reflective elements in both arrays are of equal length in the plane of rotation and normally again means are provided for combining the outputs of said two detectors in anti-phase prior to being applied for connectlon to frequency responsive means.

Preferably each focusing reflective element is a spherical reflective element.

Preferably said focusing elemental reflective elements are arranged to direct light received from the portions of the field of view on to the, or the respective, electromagnetic energy detector via an array of planar reflectors said focusing reflective elements being arranged to lie in a plane spaced from the plane in which the array of planar reflective elements lie, but with said two last mentioned planes parallel to the plane of rotation, and said focusing and planar reflective elements being tilted from the perpendicular to the plane of rotation as required to provide the energy paths from the focusing reflective elements to the detector or detectors, as required.

Preferably again a second array of planar reflective elements is interposed between said first mentioned array of planar reflective elements and the detector or detectors, said second array of planar refelective elements lying in a plane spaced from but parallel to the said plane in which the first mentioned array of planar reflective elements lie and on the side thereof remote from the said plane in which the focusing reflective elements lie, the planar reflective elements of said second array being also tilted from the perpendicular to the plane of rotation as required.The detector or detectors may lie in the same plane as the second array of planar reflective elements or in a further plane spaced from but parallel to the plane in which said second array of planar reflective elements lie and on the side thereof remote from the plane in which the first array of planar reflective elements lie.

In a practical embodiment of the invention in the above application in which the plane of rotation is the horizontal plane, said array of focusing reflective elements is arranged at one level across the rear of a housing to direct received energy in the target direction towards the front of said housing onto said first array of planar reflective elements which are arranged at a lower level towards the front of said housing, said first array of planar reflective elements is arranged to direct energy towards the rear of said housing onto said second array of planar reflective elements which is arranged at a still lower lever and said second array of planar reflective elements is arranged to direct energy towards said detector or detectors mounted towards the front of the housing at a level below that of said second array of planar reflective elements.

Preferably the axis of rotation is arranged to pass approximately through the middle of said array of focusing reflective elements.

According to this invention a range responsive apparatus comprises a plurality of energy sensitive detectors each of which is arranged to receive electro-magnetic radiation simultaneously from spaced portions of a respective field of view, means for rotating the field of view of the detectors to cause the fields of view to sweep across a target thereby producing from each detector a plurality of signals whose timing is dependent on the range of the target, means for imposing a relative delay between the outputs from different detectors and means for combining the signals for utilization.

The time delays are normally such that in operation the differences in time between each of said detectors scanning said target are compensated for such that coincidence is achieved prior to combination for utilisation. In practice the outputs of each individual energy sensitive detector may be subjected to delay although of course in the case of the last detector to scan said target said time delay may be zero.

Preferably, means are provided for adjusting the period of the or each time delay.

It is possible to provide, each of the aforementioned energy sensitive detectors in duplicate. Each such pair of detectors is arranged so that, when one detector is receiving energy from a target, the other is not; and vice versa. The signals from each pair of detectors are combined after inversion of one of them.

The invention is illustrated in and further described with reference to the drawing accompanying the provisional specification which is a highly schematic block diagram of one range responsive apparatus in accordance with the present invention.

The drawing accompanying the provisional specification may be contrasted with Figure 1 of the drawings accompanying the aforementioned co-pending application. In essence, instead of providing a single infrared detector at the point F in Figure 1 of the aforementioned co-pending application, a plurality, in this case 5, of individual detectors D1 to D5 are provided arranged so that their respective fields of view sweep across a target in sequence. Thus with rotation as represented by the arrow W about the point P first detector D1 will scan the target, then detector D2 ... and so on. The output of each of the individual detectors D1 to D5 is connected to a respective delay circuit T1 to T5, which are adjustable.The time delays of the time delay circuits T1 to T5 are set appropriately so that at their outputs the difference in time between each of the detectors D1 to D5 scanning the target are compensated for and the output signals of the time delay circuits T1 to T5 are in co-incidence when combined at point CO.

The effect achieved by the present invention corresponds to that which would be obtained by causing a single infra-red detector to scan across the target on successive rotations, whilst its output was subjected to integration. Indeed it is possible that the improved accuracy provided by the present invention is greater than that which would be obtained by integration over the number of rotations, since during such number of rotations the target itself may have moved significantly. In order to increase the "vertical aperture" of the system the array of detectors D1 to D5 may be formed into a matrix to give rise to a number of simultaneous pulse trains each representative of targets, or the target, in different vertical planes.Instead of a matrix it may be satisfactory to provide a single array of detectors, extending at right angles to the array D1 to D5 in order to provide field coverage in the vertical direction. The information provided by such an additional array may then be utilised to direct the horizontal array D1 to D5 towards any target of interest detected by the additional vertical array, for subsequent rotations.

Where, as for example the embodiment described with reference to Figures 7, 8 and 9 in the aforementioned co-pending application, two individual infra-red detector elements are provided whose outputs are combined in anti-phase by means of an inverter (reference 61 in Figure 9 of the co-pending application) each of the individual detector elements 26N and 26P would be replaced by an arrangement as schematically represented in the drawing accompanying the provisional specification.

WHAT WE CLAIM IS: 1. A range responsive apparatus comprising a plurality of energy sensitive detectors each of which is arranged to receive electromagnetic radiation simultaneously from spaced portions of a respective field of view, means for rotating the fields of view of the detectors to cause the fields of view to sweep sequentially across a target thereby producing from each detector a plurality of signals whose timing is dependent on the range of the target, means for imposing a relative delay between the outputs from different detectors and means for combining the signals for utilisation.

2. Apparatus according to claim 1 in which the delay is such as to produce coincidence between the signals from the different detectors.

3. Apparatus according to claim 1 or 2 including means for adjusting the delay.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. According to this invention a range responsive apparatus comprises a plurality of energy sensitive detectors each of which is arranged to receive electro-magnetic radiation simultaneously from spaced portions of a respective field of view, means for rotating the field of view of the detectors to cause the fields of view to sweep across a target thereby producing from each detector a plurality of signals whose timing is dependent on the range of the target, means for imposing a relative delay between the outputs from different detectors and means for combining the signals for utilization. The time delays are normally such that in operation the differences in time between each of said detectors scanning said target are compensated for such that coincidence is achieved prior to combination for utilisation. In practice the outputs of each individual energy sensitive detector may be subjected to delay although of course in the case of the last detector to scan said target said time delay may be zero. Preferably, means are provided for adjusting the period of the or each time delay. It is possible to provide, each of the aforementioned energy sensitive detectors in duplicate. Each such pair of detectors is arranged so that, when one detector is receiving energy from a target, the other is not; and vice versa. The signals from each pair of detectors are combined after inversion of one of them. The invention is illustrated in and further described with reference to the drawing accompanying the provisional specification which is a highly schematic block diagram of one range responsive apparatus in accordance with the present invention. The drawing accompanying the provisional specification may be contrasted with Figure 1 of the drawings accompanying the aforementioned co-pending application. In essence, instead of providing a single infrared detector at the point F in Figure 1 of the aforementioned co-pending application, a plurality, in this case 5, of individual detectors D1 to D5 are provided arranged so that their respective fields of view sweep across a target in sequence. Thus with rotation as represented by the arrow W about the point P first detector D1 will scan the target, then detector D2 ... and so on. The output of each of the individual detectors D1 to D5 is connected to a respective delay circuit T1 to T5, which are adjustable.The time delays of the time delay circuits T1 to T5 are set appropriately so that at their outputs the difference in time between each of the detectors D1 to D5 scanning the target are compensated for and the output signals of the time delay circuits T1 to T5 are in co-incidence when combined at point CO. The effect achieved by the present invention corresponds to that which would be obtained by causing a single infra-red detector to scan across the target on successive rotations, whilst its output was subjected to integration. Indeed it is possible that the improved accuracy provided by the present invention is greater than that which would be obtained by integration over the number of rotations, since during such number of rotations the target itself may have moved significantly. In order to increase the "vertical aperture" of the system the array of detectors D1 to D5 may be formed into a matrix to give rise to a number of simultaneous pulse trains each representative of targets, or the target, in different vertical planes.Instead of a matrix it may be satisfactory to provide a single array of detectors, extending at right angles to the array D1 to D5 in order to provide field coverage in the vertical direction. The information provided by such an additional array may then be utilised to direct the horizontal array D1 to D5 towards any target of interest detected by the additional vertical array, for subsequent rotations. Where, as for example the embodiment described with reference to Figures 7, 8 and 9 in the aforementioned co-pending application, two individual infra-red detector elements are provided whose outputs are combined in anti-phase by means of an inverter (reference 61 in Figure 9 of the co-pending application) each of the individual detector elements 26N and 26P would be replaced by an arrangement as schematically represented in the drawing accompanying the provisional specification. WHAT WE CLAIM IS:

1. A range responsive apparatus comprising a plurality of energy sensitive detectors each of which is arranged to receive electromagnetic radiation simultaneously from spaced portions of a respective field of view, means for rotating the fields of view of the detectors to cause the fields of view to sweep sequentially across a target thereby producing from each detector a plurality of signals whose timing is dependent on the range of the target, means for imposing a relative delay between the outputs from different detectors and means for combining the signals for utilisation.

2. Apparatus according to claim 1 in which the delay is such as to produce coincidence between the signals from the different detectors.

3. Apparatus according to claim 1 or 2 including means for adjusting the delay.

4. A range responsive apparatus sub

stantially as herein described with reference to the drawing accompanying the provisional specification.