Abstract:
The invention relates to a method for producing picture element groups by means of laser rays in space and on a plane. The laser ray, functioning as a picture ray, is divided into a main ray and one or more secondary rays. The secondary rays are transformed into groups of individual picture elements by adapted devices. In the pictorial representation of 3D images, secondary images arise consisting of an individual picture group made of individual picture elements.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The invention relates to an apparatus for producing picture element groups in space, to designs of such an apparatus and to methods for producing picture element groups in space as realized by such apparatus. 
   “Picture element groups” are arrangements of picture elements which are similar in geometric appearance and which can be varied with respect to location, size and orientation. They are specified by a corresponding number of parameters and produced by adapted devices in deflection systems. The picture elements of a picture element group are made into a group pursuant to a given general instruction and simplify the scope and time involved in the formation of the overall image. This results in an image with greater informational content achieved by a relatively lower amount of technical effort. 
   2. Prior Art 
   DE 2622802 C2 discloses a 3D display for generating picture elements in a cylindrical space which as a whole produce real 3D images. The term “real” here means that the spatial laser picture, in contrast to 3D representations, floats in an apparently empty space on flat screens or in stereoscopic images. It can be viewed from all surrounding directions, like a fish in an aquarium, without the help of any optical aids. Such images are commonly referred to as “volumetric 3D displays”. The 3D image in DE 2622802 is generated by projecting a laser beam at a rotating helical surface known in practice as a “helix”. For that reason, this system is designated as a “helix-laser-3D display”. 
   A helix-laser-3D display in its most simple form is shown in FIG.  1 . The laser  1  emits short light-induced pulses which are directed by a deflection system as image beam  2  onto the helix  6 , where picture elements  10  are produced. Although the picture elements at adjacent locations x,y,z, due to the continual rotation of the helix, can only be generated a completely different points of time, they are perceived by the human eye as interconnected adjacent picture elements. The helix is made of thin, translucent material such that the image beam is scattered upwards and downwards in approximately the same possible degree of diffusion. It rotates in a transparent cylinder  7  about a rotation axis  8  at a rate of 20 revolutions per second and is invisible to the viewer. The picture elements “float” in space. 
   For simple demonstrations of this principle using but a few picture elements or a loop of pre-programmed spatial images one may employ an opto-mechanical deflection system. It consists of two mirrors that can be swiveled orthogonally to one another: the x-deflection mirror  3  and the y-deflection mirror  4 . If necessary, a stationary tilted mirror  5  deflects the image beam onto the helix  6 . The x,y,z coordinates of the desired picture element are predetermined by the computer and adjust via actuators the deflection mirrors  3  and  4  for x and y, as well as a timed pulse for the height z, which is generated at the start of a light flash of the laser  1  to correspond to the rotational angle  9  of the helix. The horizontal size of the picture element is a function of the diameter of the image beam  2  and its height is a function of the duration of the flash. Dedicated applications require a very large number of picture elements, if possible with a plurality of features. Opto-mechanical deflection systems, such as the mechanical rotational mirror described here, are inadequate for this purpose. 
   For military applications, the helix-laser-3D display was built by the US Navy at great technical expense and employed for different purposes (Technical Report 1793, Revision 2, October 1998, US Navy Space and Naval Warfare Systems Center, San Diego, Calif. 92152-5001). For this purpose high-performance opto-electronic deflection systems were developed. They are capable of generating 3D landscapes consisting of more than 100,000(1) minute picture elements which are refreshed more than 20 times per second, in three colors, dynamic and with variable intensity. These helix-laser-3D displays were first used for submarine navigation, later for air-traffic control and then for medical and CAD purposes as well. 
   For non-military applications such systems are still too costly. Even the generation of a modest number of independent and randomly variable picture elements requires a disproportionately high engineering effort for the deflection system. As already mentioned, such a system must be able to direct the image beams for every single picture element at the right time onto the desired x,y,z position and have it flashed at the correct time. Here one must always keep in mind that, due to helix rotation, each x,y,z picture element can only be generated in space at a very brief and precise moment in time. This means that the 3D image must be composed point by point in temporal succession at x,y,z positions generally located far from each other. The coordination of position and time requires a very rapid change of the image beam from every x,y,z position to every other x,y,z position located at an arbitrary distance and likewise requires a very high degree of precision in stroboscope timing and duration. The efficiency of a helix-laser 3D display is gauged by how many picture elements with which variable features (color, intensity, etc.) the deflection system is able to generate with sufficient speed and compose them into a 3D scenario. The engineering effort for deflection systems increases exponentially with the number of desired picture elements. 
   The 3D images are usually composed point by point from individual picture elements. Each of these is defined by its x,y,z coordinate and by additional characteristics, which must be implemented by the deflection system. This means that every single picture element demands the same degree of effort from the deflection system regardless of its importance in the overall image. 
   U.S. Pat. No. 5,854,613 A discloses a possibility for multiplying image beams by using translucent mirrors to distribute the beams. Here the incident light beam is divided into two emitted beams having half of the light intensity, it being possible to generate a plurality of optical beams in succession with the same drop in light intensity. Each of the resulting optical beams requires its own deflection unit. Directed toward a desired x,y,z position, each sub-beam generates a single picture element in space. 
   BRIEF SUMMARY OF THE INVENTION 
   In light of the above, the object of the invention is the development of apparatus and methods to realize the generation of 3D images, i.e. picture elements in space, in the most simple and rapid manner possible. In the process this should also relieve universal deflection systems and release them for other tasks. A slightly greater engineering effort should generate an overall greater number of picture elements and in this way overcome the previous problem of bottlenecks. This would also provide the user with additional information which makes the 3D image scenario more realistic and facilitate interaction. 
   This object is realized with an apparatus for the production of picture elements in space in which
         light pulses are generated in rapid succession whose light is deflected by a deflection device in two independent orthogonal directions and directed onto a rotating projection surface on which the light pulses are visible as picture elements,   the deflection device comprises a plurality of optical deflection elements which divide the incident light into a main beam and at least one secondary beam by generating a plurality of partial beams by separating at least one part of the incident beam&#39;s cross section,   the deflection elements can be directed independent of one another and the partial beams can be influenced such that picture element groups of various kinds are generated.       

   The image beam can be divided by separating a self-contained part of the image beam&#39;s cross-section or by sifting out a portion of the image beam. After division, the secondary beam is subjected to various processes. This results in various kinds of picture element groups: those which undergo serial composition (successively in time) and appear to the viewer as blinking lights, and those which arise in parallel (simultaneous) fashion and appear to the viewer as being stationary. The picture element groups thus generated form the secondary images. The main image and secondary image taken together form the overall image. The viewer sees the overall image as a unit in which the main image can appear dominant, while the secondary image can stand out, for example, by virtue of the deliberately smaller size of its picture elements or by having blinking elements. Such features can be used to advantage for accompanying supplementary information. 
   The method pursuant to the invention should preferably be employed for applications capable of functioning with relatively few picture elements and which are suitable for the use of macro images, such as air-traffic control and CAD. Such applications have already been emphasized in DE 2622802. 
   The helix-laser 3D display was already used in the USA for air-traffic control in the Navy. There the entire flight scenario was composed by individual points in the cylinder. Newly added to this process is now the invention&#39;s use of secondary images which can symbolize flying objects, for instance, in the form of picture element patterns or show flight paths and flight speeds in the form of line elements. Furthermore, secondary images can be generated in the form of two-dimensional images of all flight activity on the base or lid of the cylinder which can be supplementally used interactively in conjunction with markings or variable map projections. Furthermore, objects in flight can be marked in space, i.e. with little additional effort, their position can be highlighted by means of appropriate macro images and/or by blinking and can therefore be recognized quickly. 
   Advantages are also presented for CAD applications because the computer geometry, on which CAD is based, is determined essentially by line elements and vectors. Macro images used in this branch can be represented by the picture element groups described here, thus making images more vivid and facilitating human-machine interaction. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     The exemplary embodiments of the invention will be described in more detail in the following by means of drawings which show 
       FIG. 1  basic prior art 
       FIG. 2  apparatus for producing horizontal linear picture element groups 
       FIG. 3  compact embodiment of apparatus shown in  FIG. 2   
       FIG. 4  apparatus for producing horizontal circular picture element groups 
       FIG. 5  apparatus for producing vertical linear picture element groups 
       FIG. 6  apparatus for producing horizontal picture element groups as symbols 
       FIG. 7  apparatus for producing 2D copies of picture element groups, 
       FIG. 8  combined application of different apparatus 
       FIG. 9  shows how a number of the described apparatus interact. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The apparatus pursuant to  FIG. 2  comprises a x-deflection mirror  3  and a y-deflection mirror  4 , which has a cutout  11  in the middle. Part of the image beam reflected by the deflection mirror  4  is reflected by the y-deflection mirror  4  as a main beam  12 , while another part of the image beam is reflected by the secondary mirror  14  as a secondary beam  13 . This secondary mirror is swivel-mounted in the rotation axis  15 , which in turn rests in a ring  16  that can swivel orthogonally and with which the axis  15  can be turned. The light beams  12  and  13  run parallel to each other as long as the reflection planes of the mirrors  4  and  14  are aligned parallel to each other. Any twist of the mirror  14  about the rotation axis  13  or with the ring  16  alters the secondary beam  13 , producing an independent picture element on the helix corresponding to its relative position. Proceeding from small twist increments  15  and  16 , this additional picture element lies near the picture element produced by the main beam  12 . Its size depends on the opening of the cutout  11 . 
   This makes it possible to represent line segments of element groups on the helix. Their direction is determined by the position of the ring  16  and their length is determined by the extent of oscillation amplitude of the mirror  14  about the rotation axis  15 . They can originate in the picture element produced by the main beam  12 . They would thus appear as 3D vectors, similar in appearance to the vapor trails of a jet airplane. For flight-controllers, they can be seen as representing the speed and direction of an aircraft. 
   The oscillation of the secondary mirror can and should be constant, but independent of the rotation speed of the helix. The light flashes for the main beam and secondary beam  13  are identical. By forgoing any synchronization here, the partial picture elements appear in statistical distribution between the positional limits. This causes a line element marked by minutely flickering light flashes to appear in addition to the strictly stationary main picture element at the x,y,z position. For flight-control applications, the intensity of the light flashes can be set by the size of the cutout  11  and the appearance of the vapor trails can be set by the oscillation frequency of the rotation axis  15 . The view of the elements in  FIG. 2  has been deliberately exploded for easier understanding. In practice they are arranged as closely as possible. 
   The apparatus pursuant to  FIG. 3  represents an arrangement in which the aforementioned elements lie on one plane. By virtue of cardanic mounting  17 , all elements can be independently adjusted with respect to their functional operations described above. The direction and amplitude of oscillation can be determined by means of a connector oriented along the mirror axis  18  and the spring-mounted rotating ring  19 . Advantageous here is the compact design and the avoidance of multiple beam switching which are always associated with a loss of precision and light intensity. 
   The apparatus pursuant to  FIG. 4  represents an arrangement that can be used as a 3D mouse. The image beam  2  strikes a rotating mirror  22 , which is driven by the motor  21  and whose normal mirror line deviates slightly from rotation axis of the motor  21 . This creates in the reflection a image beam circle  23  which is projected via the tilted mirror  5  onto the helix  6 , where is produces a circular mouse pointer  20  around the picture element  10 . Guided by hand with a 3D input device, such a mouse pointer can be moved to any x,y,z position in the cylinder  7 . A numerical comparison with the programmed sequence of images in the cylinder determines which, if any, of the graphically displayed objects is momentarily targeted by the mouse pointer. 
   The apparatus pursuant to  FIG. 5  represents and arrangement that produces line segments in the direction of the image beam  12 . They can be of any length and may lie above as well as below the position of the main picture element. This is achieved as follows. The image beam reflected by the deflection mirror  3  is divided at the deflection mirror  4 . Deflection mirror  4  and secondary mirror  24  reflect the main beam  12  and the secondary beam  13 . Since both mirrors are coupled, the main beam  12  and the secondary beam  13  always remain parallel to each other. Both beams are provided with separate diaphragms  25  and  26 . An open diaphragm allows the continuously radiating laser beams to pass. The diaphragm  25  at main beam  12  is only opened temporarily, thus producing the picture element  10 . The diaphragm  26  at the secondary beam, in coordination with the rotational movement of the helix, can be open at any time and for any duration. For example, if the diaphragm  26  is open while the helix at the predetermined x,y,z position runs from where the height z=0 to the predetermined height z, the secondary beam then produces a line from the base of the cylinder to the x,y,z point. By causing the diaphragm  26  to oscillate during this time, a dashed line is produced. In practice the beams  12  and  13  must be directed very close to one another or merge with one another. 
   The apparatus pursuant to  FIGS. 6 and 7  represents an arrangement which produces picture element groups whose picture elements are generated in parallel (simultaneous) fashion. In this case, image beam splitters made from linear optical elements are employed. In this example, the image beam splitters are composed of planar facets  28  or linear facets  28   a . The image beam  2  strikes the image beam splitter in the direction of the main beam  12  and is split. The main beam  2  passes unimpeded through the optically inactive region provided in accordance with its size, while at the same time a separate secondary beam is produced at each facet lying in the beamed region. The orientation of each facet can be predetermined separately and thus also the deflection of the associated secondary beam with respect to the main beam  12 . In this manner, picture element groups can be produced as patterns. A convex lens  27  merges the secondary beams to create a secondary beam cluster  29  which runs in the direction of the main beam  12  and which represents a picture element symbol  30  in addition to the picture element  10 . The picture element symbol can be enlarged and reduced by a revolver-like change of convex lenses  27 . It can be rotated by rotating the image beam splitters  28  about the main beam  12 . In a limit case of this example, the image beam splitter  28   a  can be a cylindrical lens, thus turning a linear arranged picture element group into a continual line. The exemplary image beam splitter shown here can, in a limit case, be turned into one or more open or closed curved arrangements, which in a special case can also be one or more circles. 
   The apparatus pursuant to  FIG. 8  represents an arrangement used to turn the 3D image into a picture element group which depicts a 2D projection of the 3D image. For this purpose, the helix  6  in the cylinder  7  is designed as a finely woven net and acts as a planar image beam splitter. Every 3D image produced on the helix  6 , for example comprising a central picture element  10  and an accompanying picture element symbol  30 , then appears in the extension of the main beam as a 2D copy  21  in this example on the bottom of the cylinder. 
   The apparatus pursuant to  FIG. 9  shows how a number of the apparatus described above interact. Because deflection systems were normally unable to generate any number of picture elements, such application were hitherto limited to the representation of objects in the form of individual picture elements or as a cluster of such picture elements  10 . 
   3D scenarios can now be represented by picture element groups in a more informative manner. Thus, in addition to a main image, a picture element symbol  30 , for example in the form of an arrow or airplane, can be shown with respect to size and direction (cf. FIG.  7 ). At the same time a linear picture element group can represent a flight direction vector  34  for direction and velocity (either according to  FIG. 3  or FIG.  6 ). A flight altitude vector  35  can also be represented (cf. FIG.  5 ). At the same time, the 2D copies  32  and  33  of the entire 3D image can be generated (cf. FIG.  8 ). They can appear as shown here on the cylinder bottom  31  while a map  36  is projected there at the same time. This can also be projected through an open cylinder bottom  31  onto a remote map  36  located below it. At the same time an independent picture element group, serving as a mouse pointer  20 , can be manually guided in the cylinder (cf.  FIG. 4 ) and call up information from the computer about an object it clicks on. A 2D copy of this also appears at the bottom of the cylinder. Parallax deviations can be kept to a minimum by using long beam paths, which can be tolerated anyway in applications having an image space that is not greatly occupied. 
   This makes it possible to produce a 3D representation of flying objects in space and at the same time present them as a 2D image in an interchangeable map, for example one projected from below.