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Title: Head-up display units and optical devices
Claims: I claim: 1. A head-up display unit for use for example in an aircraft including a luminous data signal producing means for producing collimated luminous data signals, combining means for receiving light rays from said signal producing means and for combining them with light rays received from a distant scene which is to be observed at a predetermined observation position whereby to enable the said scene and data signals to be observed at the said observation position in superposed relationship, characterised in that at least a part of the said signal producing means is disposed between the said observation position and the said scene and hence obscures direct observation of at least a part of the said scene as viewed from the said observation position, and the combining means is disposed between the said signal producing means and the said observation position and includes optical means having light transmissive and light reflective properties for producing at the said observation position an image of the said scene ahead as viewed from a position spaced transversely of the said signal producing means and an image of the said luminous data signals, one of those images being produced by virtue of the said reflective properties of the optical means and the other of those images being produced by virtue of the said transmissive properties of the optical means. 2. A head-up display unit according to claim 1, wherein the said optical means produces at the said observation position images of the said scene ahead as viewed from separate positions spaced transversely apart on opposite sides of the said signal producing means, as well as the image of the said luminous data signals, the respective images of the said scene ahead being produced by virtue of the same type of optical properties of the said optical means. 3. A head-up display unit according to claim 1 characterized in that the luminous data signal producing means includes a source of luminous signals, and a collimating optical unit having a part defining an input aperture disposed adjacent the luminous signal source and a part defining an output aperture or porthole through which a virtual image of the luminous signal source is visible, which image subtends at the eye of an observer; when looking at the porthole from a predetermined eye position, a predetermined angle that is greater than the angle subtended by the porthole at the observer's eye, and that at least the porthole part of the collimating optical unit is disposed between the said observation position and the said scene ahead of the observer whereby part of the observer's view of that scene by direct vision is obscured, and that the combining means is disposed between the porthole part of the collimating optical unit and the said observation position, and comprises means for transmitting to the observer's eye a view of the porthole by direct transmission of light from the porthole and a view of the said scene ahead by reflection of light from the said scene. 4. A head-up display unit according to claim 3, wherein the combining means includes at least one first plane optical face disposed adjacent the porthole and inclined at an angle thereto, and at least one second plane optical face disposed substantially parallel to but spaced from the first optical face, the first optical face being capable of transmitting light from the porthole to an observer at the observation position and of reflecting to the observer light received from the scene ahead by virtue of reflection at the second optical face. 5. A head-up display unit according to claim 3, wherein the combining means includes two mutually-inclined plane optical faces (referred to hereafter as the inner optical faces) which adjoin one another at a common edge disposed remote from the said porthole part, which inner optical faces diverge in the direction of and jointly span the said porthole part, and two further plane optical faces (referred to hereafter as the outer optical faces) which are disposed substantially parallel with and spaced from the respective inner optical faces, the inner optical faces being capable of transmitting light from the porthole to an observer at the observation position and of reflecting to the observer light received from the scene ahead by virtue of reflection at the outer optical faces. 6. A head-up display unit according to claim 5, wherein the inner and outer optical faces have edges which lie in a common plane adjacent the porthole part. 7. A head-up display unit according to claim 3, wherein the said common edge of the inner optical faces is positioned centrally relative to the part of the collimating optical unit which obscures the observer's direct vision of the scene ahead; the inclination and length of each inner optical face, and the inclination and spacing of each outer optical face relative to the adjacent inner optical face, are determined by the path of a predetermined boundary ray of light which passes from a predetermined extremity of the scene ahead on one side thereof and which is seen by an observer's eye positioned at a predetermined limiting eye position on the opposite side of a central plane which passes through the said common edge of the inner optical faces and through the center of the said porthole part and of the scene ahead, after reflection at the respective edges of the inner and outer optical faces which lie nearest the said porthole part on the same side of the central plane as the said extremity; and the length of each outer optical face being determined by the path of a limiting ray of light from the scene ahead, which ray skirts the said vision-obscuring part of the collimating optical unit on the same side of the central plane as the said predetermined limiting eye position, and which is seen by the observer's eye at that position after reflection at the respective edges of the outer and inner optical faces which lie furthest from the said porthole part on the same side of the central plane as the said limiting eye position. 8. A head-up display unit according to claim 5, wherein each inner optical face has a central area which is capable of transmitting light to the observer directly from the porthole and by reflection from the adjacent outer optical face, and boundary areas which adjoin the central area and which are capable of transmitting light to the observer only by reflection from the adjacent outer optical face. 9. A head-up display unit according to claim 5, wherein inner and outer optical faces which lie adjacent one another are constituted by opposite, substantially parallel faces of a glass prism, and wherein a third glass prism of triangular shape has two similar plane faces cemented to the respective faces of the respective prisms which constitute the said inner optical faces, the cemented pairs of faces of the third prism being such as to provide the aforesaid light transmitting and reflecting properties, and the three prisms being of a glass material having predetermined optical properties. 10. A head-up display unit according to claim 9, wherein the two prism faces nearest the said observation position and through which the observer may perceive the scene ahead and the luminous signals are disposed in a common plane which is parallel with the plane of the porthole. 11. A head-up display unit according to claim 9, wherein each prism face constituting one of the said outer optical faces has cemented thereto a plane face of a glass prism of triangular shape, whereby to provide an assembly of five prisms in which the cemented faces which constitute the outer optical faces are arranged to be capable of transmitting light from the scene ahead directly to the observer, and by reflection to the adjacent inner optical face, the respective prism faces of the assembly which are nearest the said observation position being disposed in a common plane which is parallel with the plane of the porthole and the outer triangular prism being of a glass material having the said predetermined properties. 12. A head-up display unit according to claim 9, wherein the two similar faces of the central triangular prism are treated before being cemented to adjacent faces of adjacent prisms so as to render them capable of transmitting light from the porthole and of reflecting light from the adjacent outer optical face, and wherein each of the said adjacent faces of the said adjacent prisms is similarly treated as aforesaid only at a central area, and is treated at boundary areas adjoining the central arm so as to render the boundary areas only capable of reflecting light from the adjacent outer optical face. 13. A head-up display unit according to claim 9, wherein in the assembly of prisms the inner and outer optical faces terminate at plane transverse faces which diverge in the direction of the porthole. 14. A head-up display unit according to claim 4, wherein the plane optical faces are constituted by surface areas on plates of glass, which areas have been treated to give them the required optical properties, the plates of glass being rigidly carried in a supporting means. 15. A head-up display unit according to claim 3, wherein the input aperture of the collimating optical unit is coaxial with the output aperture or porthole. 16. A head-up display unit according to claim 3, wherein the input aperture of the collimating optical unit is offset relative to the output aperture or porthole, and the collimating optical unit includes means for reflecting rays of light from the luminous signal source to the porthole whereby to render luminous signals of the said source visible through the porthole. 17. A head-up display unit according to claim 15, wherein the collimating optical unit has a second input aperture disposed adjacent a second luminous signal source, and the collimating optical unit includes means for combining rays of light from the respective luminous signal sources whereby to render luminous signals from both sources visible simultaneously through the porthole. 18. A head-up display unit according to claim 3, wherein the, or at least one, luminous source includes electrical energisation means responsive to electrical input signals supplied thereto whereby to provide a luminous signal display which varies in accordance with the input signals. 19. A head-up display unit according to claim 3, wherein the, or at least one, luminous signal source comprises means for producing a static display of luminous signals. 20. A head-up display unit according to claim 18, wherein the, or at least one, luminous signal source comprises a cathode ray tube. 21. A head-up display unit according to claim 3, wherein an output lens mounted at the porthole comprises a lens in the shape of a circle from which opposite edge parts have been removed to provide a pair of parallel boundaries. 22. A head-up display system including a head-up display unit according to claim 18, electrical amplifying means having output circuit means connected to the luminous signal source whereby to supply thereto electrical signals for varying the display of luminous signals, electrical computing means having output circuit means connected to the amplifying means whereby to supply thereto electrical control signals for varying the luminous signals display in accordance with a predetermined function of input signals supplied to input circuit means of the computing means. 23. An aircraft having a head-up display unit according to claim 3 mounted adjacent a windshield. 24. An aircraft having mounted therein a head-up display system according to claim 22. 25. A head-up display unit for use for example in an aircraft or other vehicle comprising a data source operable to present luminous data signals; a collimating optical system at least part of which, when the display unit is being carried in or by a vehicle, intercepts the line of sight of the observer to the distant scene forward of the observer and which is effective to project collimated luminous data signals presented by the data source; and, between an output porthole of the collimating optical system and the observer, first and second partially light-transmissive, partially light-reflective planar films which are so inclined to one another as to define a space in the form of a prism of triangular cross section which spans the porthole and the apical edge of which is remote from the porthole, and through which such luminous data signals as may be projected from the porthole are transmitted to the observer, and third and fourth light reflective planar films parallel to and laterally spaced with respect to the first and second films, respectively; and in which, the angle of inclination between the first and second films is such, and the dimensions of the four films, and the lateral spacing between the first and third films and the second and fourth films, respectively, are such that certain rays of light from the distant scene forward of the observer and incident on the third film are received by the observer after successive reflections at the third and first films, in like manner certain rays of light from the distant scene forward of the observer and incident on the fourth film are received by the observer after succession reflections at the fourth and second films, and light reflected from the said part of the collimating optical system and incident on the third and fourth films, and after reflection therefrom, on the first and second films respectively, is deflected by the first and second films so that, for a certain range of movement of the observer's head in either direction transverse to the forward line of sight of the observer, the said part of the collimating optical system is not visible to the observer. 26. A head-up display unit according to claim 3, wherein the outer optical faces are supported separately from the associated inner optical faces. 27. A head-up display unit which comprises a luminous data source, and between that source and an observer's observation position a beam-splitting periscopic device which is effective to deflect rays from that part of a scene ahead of the luminous data source which in the absence of the periscopic device would be obscured by the luminous data source, in such manner that the said part of the scene ahead is reconstituted at a position between the data source and the observation position, so that an observer at the observation position would have a substantially uninterrupted and undistorted angular field of view of the scene ahead superimposed upon the luminous data transmitted by the periscopic device. 28. An optical device for use by an observer for the purpose of obtaining an unobstructed field of view of a forward distant scene in the presence of an obstruction lying within the aforesaid field of view, which device has first and second light-reflective planar films which are so inclined to one another as to define a space in the form of a prism of triangular-cross-section the base of which has a width not less than the width of the said obstruction; and third and fourth light-reflective planar films parallel to and symmetrically and laterally spaced with respect to the first and second films respectively; in which device the angle of inclination between the first and second films, the dimensions of the four films, and the lateral spacing between the first and third film and the second and fourth films, respectively, are all such that, when, in use, with the device supported so that the said obstruction is spanned by the first and second planar films certain rays of light from the distant scene forward of the observer and incident on the third film are received by the observer after successive reflections at the third and first films, and in like manner certain rays of light from the distant scene forward of the observer and incident on the fourth film are received by the observer after successive reflections at the fourth and second films; light rays from the distant scene which are reflected by the obstruction and are incident on the third and fourth films and, after reflection therefrom, on the first and second films respectively being deflected by the first and second films so that, for a predetermined range of movement of the observer's head in either direction transverse to the forward line of sight of the observer to the distant scene, the said obstruction is not visible to the observer; and in which device the transverse distance between the third and fourth films at their edges which are closest to the observer's viewing position is not less than a predetermined inter-pupillary distance of the observer, and for the said range of observer's head movement the width as seen by the observer of each of the third and fourth films is not greater than the said inter-pupillary distance. 29. An optical device comprising a glass prism assembly which includes three prisms of glass material of the same optical properties cemented together, the prisms comprising a. a central prism of triangular transverse cross section defined by two similar, plane, light-outlet faces and a plane, light-inlet face inclined at equal angles to the respective light-outlet faces, and b. two similar outer prisms disposed side to side and symmetrically adjacent the respective light-outlet faces of the central prism, each outer prism having parallel, plane, input and output reflective faces, of which the output reflective face is cemented to the adjacent lightoutlet face of the central prism to form an interface between the respective prisms, at least a central area of the interfaces being partially light-reflective and partially light-transmissive, and plane, light-inlet and light-outlet faces disposed parallel to one another and to the light-inlet face of the central prism so that when in use an observer looking at the adjoining light-outlet faces of the outer prisms observes simultaneously i. a distant scene ahead of the assembly through the light inlet and outlet faces of the respective outer prisms, by virtue of the reflection of light rays from that scene successively at the input and output reflective faces in each other prism, and ii. any bright object disposed immediately ahead of the light inlet face of the central prism by virtue of the direct transmission, without any substantial refraction, of light rays from that object through the said interfaces, so that the observer sees an image of the said scene ahead with an image of the said object superposed thereupon. 30. An optical device according to claim 29, wherein the partially light-reflective and partially light-transmissive central area has adjoining it interface boundary areas which are light-reflective only. 31. An optical device comprising four plane glass plates, and means supporting those plates rigidly in predetermined positions, an inner pair of said plates (hereafter called the inner plates) being disposed in V-formation with their outwardly-facing plane surfaces meeting one another at a common linear edge and carrying thin optical coatings which render those surfaces partially light-transmissive and partially light-reflective, and the plates constituting an outer pair of said plates (hereafter called the outer plates) being respectively disposed symmetrically on either side of the inner pair of plates, each outer plates being disposed parallel with but spaced transversely from the adjacent inner plate, so that when in use an observer looking at the coated outwardlyfacing plane surfaces of the inner plates observes simultaneously a. a distant scene ahead of the assembly of glass plates by virtue of the reflection of light rays from that scene successively at the outer plates and the inner plates and b. any bright object disposed immediately ahead of the inner pair of plates by virtue of the direct transmission of light rays from that object through the inner plates and their optical coatings, so that an observer sees an image of the said scene ahead with an image of the said object superposed thereupon. 32. An optical device comprising two similar periscope-like elements each comprising means defining parallel-disposed, spaced, planar, light reflective, `light input` and `light output` optical faces, the two elements being arranged in reverse relationship relative to one another on either side of a central plane of symmetry, with the respective light input faces spaced transversely apart on either side of the said plane, and with the respective light output faces adjoining one another at a common linear edge which lies in the said plane, and supporting means for the said optical face defining means, the supporting means being arranged so that each eye of an observer looking at the light output faces whereby to observe through the device a distant scene lying ahead of the device in the direction of the said plane can see, and scan from side to side without interruption, both light output faces. 33. An optical device according to claim 32, wherein the said light output optical faces carry thin optical coatings which render those optical faces partially light-transmissive as well as light-reflective, so that in use an observer looking at the light output faces whereby to observe the said scene ahead through the device sees superposed upon an image of the said scene ahead an image of any bright object which is disposed immediately ahead of the light output faces. 34. An optical device according to claim 32, wherein the light input and light output faces of each periscope-like element are constituted by opposite, substantially parallel faces of a glass prism, and wherein a third prism of triangular shape has two similar plane faces cemented to the respective faces of the respective prisms which constitute the said light output faces. 35. An optical device according to claim 34, wherein the cemented faces of the respective prisms are partly lighttransmissive so that an observer looking at the said light output faces whereby to observe the said scene ahead through the device sees superposed upon an image of the said scene ahead an image of any bright object which is disposed immediately ahead of the said third prism. 36. An optical device according to claim 32, wherein the transverse distance between the edges of the light input faces which lie closest to a said observer is not less than a predetermined inter-pupillary distance of said observer, and for a predetermined range of movement of the observer's head in either direction transverse to the forward line of sight of said observer to the distant scene ahead, the transverse width of each of the light input faces, as seen by said observer, is not greater than the said inter-pupillary distance. 37. A head-up display unit according to claim 5, wherein the plane optical faces are constituted by surface areas on plates of glass, which areas have been treated to give them the required optical properties, the plates of glass being rigidly carried in a supporting means. 38. A head-up display unit according to claim 5, wherein the input aperture of the collimating optical unit is offset relative to the output aperture or porthole, and the collimating optical unit includes means for reflecting rays of light from the luminous signal source to the porthole whereby to render luminous signals of the said source visible through the porthole. 39. A head-up display according to claim 9, wherein the input aperture of the collimating optical unit is offset relative to the output aperture or porthole, and the collimating optical unit includes means for reflecting rays of light from the luminous signal source to the porthole whereby to render luminous signals of the said sources visible through the porthole. Other info: Inventors: Ellis, Stafford Malcolm Application Number: 475107 Filing Date: 1974-05-31 Publication_date: 1976-02-03 Assignee: Primary Class(es): 359/630 340/971, 340/980, 348/832, 353/12, 359/834 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Grimm, Siegfried H. Assistant Examiner: Attorney: Brisebois & Kruger |
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