DE102006006753B4 - Method for the holographic detection of movements in a holographic representation - Google Patents

Abstract

Method for the detection of reflective objects by holograms, characterized in that the surface to be detected in a holographically generated, three-dimensional light pattern when moving through this pattern generates a characteristic change in the scattering intensity analogous to the pattern intensity, so that from the position of the three-dimensional pattern and the temporal Course of the backscatter intensity conclusions about the different physical quantities of the movement (location, speed and direction) of the object are possible. The extent of the light pattern is restricted by shaping the object beam in a manner analogous to the imaging of an image with a restricted focus area. The detection is carried out by the wave complex-conjugate to the reference beam, i.e. returning in the reverse direction to the reference beam, which is caused by the reflection of the focal point of the image and its backscattering into the hologram, whereby the backscattered light is analyzed by an intensity measurement and by a clear coding, which is generated by the holographically generated light pattern, leads to an assignment of the addressed image area, the light source being used for detection.

Description

field of use

The invention relates to a method for spatial movement detection of reflecting or light-scattering bodies by means of holograms and the possible combination with a holographic representation according to the claims mentioned.

State of the art

The three-dimensional location detection of reflecting bodies is possible through many processes, the process of triangulation, strip triangulation (for example DE 196 08 632 B4 , CA 2 475 391 A1 ), the stereoscopic measurement by cameras or by runtime measurements of a scanning laser beam. In particular, the combination of such techniques with that of holographic representation is in US 63 77 238 B1 has been described. The holograms described there are the representation of virtual keypads floating in the air, in which the user can control other devices by seeming to touch these keypads. The method combines a three-dimensional, holographic representation with a three-dimensional detection technique that is constructed separately from it.

In US 2005/0 002 074 A1 becomes the idea of a holographic input plane from the patent described above US 63 77 238 B1 further developed, it describes the combination of various methods for detection and display.

An input field projected onto a surface using optical methods with optical detection of the user input is shown in US 2002/0 075 240 A1 described, here the input surface is not displayed holographically, but as a projection onto a surface. However, according to the invention, the projection beam can be generated by means of diffractive elements.

A location and speed detection by means of holographic or interferometric methods, which use the phase of a backscattered light wave for location or speed detection of objects, is described by way of example in the following methods.

So is the patent US 35 11 569 A the speed of objects is determined by phase detection of the Doppler shift, with a second frequency-shifted light source being used for superimposition. In DE 199 46 262 A1 the speed of scattering particles is determined by a holographic image of the backscatter waves at at least two positions.

In the patent US 53 78 888 A the continuous electronic recording of the hologram of an object is used to track the object via a back projection of the conjugate image wave by means of a spatial light modulator onto the object

1. 1. Depending on the selection of the detection technique, it is difficult to adapt the input page perfectly to the displayed virtual object. For example, the use of IR distance sensors only allows fine control of the distance, but not precise detection perpendicular to it, as would be required, for example, by a slider. In addition, the number of usable detection areas is heavily dependent on the detector technology used and thus also represents a significant cost factor in the construction of virtual control panels.
2. 2. Due to the separate structure of the output and input unit, it cannot be physically ruled out that unnoticed incorrect inputs are possible due to a misalignment of the hologram, the reference beam or a disruption of the detection unit. Entries correctly carried out by the user with regard to the display could lead to results other than those intended. This is a major disadvantage, especially in areas with increased security requirements (medicine, password entry, work areas with possible personal danger).
3. 3. When switching the holographic display by multiplexing (see attached patent application: method for displaying interactive content, Marcus Werner, Mechernich), either a separate detection device or a detection of the movements in the entire operating area is necessary for each of the displayed objects. In this situation, there is the additional risk that input events can be assigned to the wrong display holograms due to the loss of synchronization of the display and detection unit.

Object of the invention

• • Die eindeutige Detektion eines Körpers oder seiner Bewegung in einem bestimmten Bereich eines Hologramms durch ein im Hologramm integriertes Verfahren möglich ist.
• • Eine beliebige Anordnung, Form, Richtungsselektivität und Zahl der Detektionsbereiche möglich ist.
• • Gleichzeitig zur Detektion die Darstellung von Inhalten mit dem gleichen holographischen Medium, also eine Superposition von Detektions- und Ausgabehologramm möglich ist.
• • Die Zuordnung verschiedener holographischer Eingabeebenen zu den Darstellungsebenen so miteinander verbunden werden kann, das Zuordnungsfehler (z.B. durch Softwarefehler der Steuerelektronik) physikalisch ausgeschlossen sind.

The object of the invention is to enable the detection of surfaces by a hologram in such a way that

• • The unambiguous detection of a body or its movement in a specific area of a hologram is possible using a method integrated in the hologram.
• • Any arrangement, shape, directional selectivity and number of detection areas is possible.
• • Simultaneously with the detection, the display of content with the same holographic medium, that is, a superposition of detection and output holograms, is possible.
• • The assignment of different holographic input levels to the display levels can be linked to one another in such a way that assignment errors (eg due to software errors in the control electronics) are physically excluded.

Solution of the task

Any desired shaping of the reconstructed light wave is possible by means of holograms. In particular, light waves with high divergence (corresponding to a high aperture of the hologram) can be used to generate patterns that are only sharply displayed in a small image area, but “blur” in all other image areas due to the optical blurring. This can be achieved, for example, by imaging a two-dimensional image with a lens, the image of the image is then only sharp at a certain distance, whereby the tolerance range can be determined via the aperture of the optics (this corresponds to the forographic term depth of field). If such an image is recorded holographically, the described properties are retained without the need for the recording apparatus (image template with code sequence, lens) for playback.

These patterns should now be designed in such a way that a clear reflection signal is generated for identification when passing through a reflective surface. This is similar to the process of scanning a barcode, the three-dimensional pattern is the barcode, the object is the scanner, so to speak. The signal is analyzed by measuring the intensity of the backscattered light and, by means of a clear coding, leads to an assignment of the addressed image area. Statements can also be made about other parameters such as speed or acceleration or the direction of movement. In the following we refer to such coded areas as “focused coding area”, abbreviated as FKB .

1. 1. Nur Reflektionsignale aus dem Bereich des Brennpunktes werden in eine komplex-konjugierte Welle umgewandelt die parallel zum Referenzstrahl in entgegengesetzter Richtung verläuft.
2. 2. Der zur Detektion eingesetzte Sensor kann stets an der gleichen Position aufgestellt werden, da unterschiedliche Stellen eines FKB in den gleichen Refcrenzstrahlwinkel zurückgeworfen werden. Daher ist eine perfekte Fokussierung des rücklaufenden Strahls (z.B. durch Auskoplung mit einem teildurchlässigen Spiegel und anschließender Fokussierung auf den Detektor) möglich.
3. 3. Die Lichtquelle selbst kann zur Detektion eingesetzt werden. So kann die zur Leistungsregelung verwendetet „Monitordiode“ eines Halbleiterlasers zur Detektion herangezogen werden, oder die Rückwirkung der Interferenz zwischen der hin- und der zurücklaufenden Welle auf den Stromverbrauch eines Halbleiterlasers.

Holograms are particularly suitable for the detection method described. If a representative hologram forms an object wave with a focal point, rays returning from this focal point are deflected again by the hologram in the direction of the reference beam. This is due to the physical properties of a hologram which, when illuminated with the complex-conjugate object wave (corresponds to the time reversal of the light wave), generates a complex-conjugate reference beam. Normally, the representation of complex-conjugate waves is very expensive, but when reflecting focal points of an image, the reflected beam always corresponds to the complex-conjugate wave, since the reflection of such a spherical wave at the focal point again represents a spherical wave with the same focal point position. There FKB 's can be understood as a collection of focal points on a certain path, the described holographic possibility of using a complex-conjugate reference wave for detection ensures a particularly high signal-to-noise ratio, because:

1. 1. Only reflection signals from the area of the focal point are converted into a complex conjugate wave that runs parallel to the reference beam in the opposite direction.
2. 2. The sensor used for detection can always be set up in the same position, since one is in different places FKB be reflected in the same reference beam angle. Therefore a perfect focusing of the returning beam (eg by coupling out with a partially transparent mirror and then focusing on the detector) is possible.
3. 3. The light source itself can be used for detection. For example, the “monitor diode” of a semiconductor laser used for power control can be used for detection, or the effect of the interference between the forward and backward waves on the power consumption of a semiconductor laser.

advantages

1. 1. Due to the three-dimensional properties of the holographic image and the high available aperture, any design and arrangement of the FKB 's possible. By arranging the FKB not only a movement carried out perpendicular to the hologram surface, but also a movement carried out in parallel generate a unique code sequence. In addition, you can FKB Design in such a way that only a certain movement, for example with defined start, intermediate and end points, over a prescribed minimum distance generate a certain code.
2. 2. If the "display hologram" is recorded together with the "decoding photogram", the display and decoding can only be reconstructed at the same time and are thus inseparably linked. A user of an interactive system can thus be sure that his inputs correlate exactly with the objects displayed for orientation.
3. 3. The code signal can be detected by measuring the energy returning in the reference beam, since the wave returning from a focal point is reflected back exactly in the direction of the reference beam by the hologram for physical reasons. This guarantees that the signal has a high signal-to-noise ratio. In addition, selective signal analysis is possible in the case of holographic representations that use several reference beams for reconstruction.
4. 4. Because of the high aperture, the decoding hologram only needs to use a low light intensity in order to obtain detectable backscattering. This lowers the light requirement and thus allows, for example, almost the entire light output to be used for the possible representation of three-dimensional objects used for orientation.
5. 5. The actual dimensions of a decoding area are only limited by the resolution limit of the holographic representation. Since the holographic representation is possible in almost diffraction-limited quality through the use of narrow-band light sources, the space required for a “bit” is in the order of magnitude of the light wavelength. The FKB can therefore have expansions from the sub-mm range to the full hologram expansion. Since the FKB can be so small that the observer cannot perceive them as a code structure, they can also simply be used as part of the image of the objects represented by the hologram and thus "hidden" in the object.
6. 6. The number of unambiguously decodable areas is limited, but with a bit number of 100, corresponding to 2 ¹⁰⁰ = 1.2 * 10 ³⁰ different encodings, with a required expansion of the FKB of less than 1/10 mm. With such codes, encryption can be used to prevent guessing of code sequences. The large coding space also enables different coding sequences to be recorded simultaneously in one receiving channel, because the superimposition of different codes can be mathematically developed through the differentiation between valid and invalid code sequences. Thus, the use of the FKB the construction of a three-dimensional scanner, e.g. for face recognition or for three-dimensional drawing with the finger.
7. 7. To avoid unauthorized access, e.g. through sequences irradiated by extraneous light sources, the reference beam can be modulated with a randomly generated code, which enables unambiguous identification of extraneous light sources due to the lack of this additional coding.

Embodiments

In drawing I is the arrangement of a hologram with a holographic representation and an embedded one FKB shown. The representation of the FKB is shown greatly enlarged to visualize the code structure. The reference beam emanating from the light source L illuminates the hologram H . This creates the virtual touchpad VT and the Focused Code Area FKB reconstructed. An object moves G through the area of the FKB becomes the backscattered light RS via the hologram into a complex conjugate reference wave KK recoded and via the partially transparent beam splitter into the detector D. reflected. The intensity corresponds to that of the im FKB stored code sequence when the object moves at a steady speed from the point A. to the point B. is moved.

In drawing 2, the combination of three is exemplary FKB ( A. , B. and C. ) and the associated code sequences that can be generated are shown. A limitation in the three-dimensional arrangement of the number and the design of the touch fields is only given by the display options of the hologram and the available code space. The representation and decoding of a virtual keyboard in the same way as a PC keyboard is possible with standard holograms, for example.

Claims (5)

Method for the detection of reflective objects by holograms, characterized in that the surface to be detected in a holographically generated, three-dimensional light pattern when moving through this pattern generates a characteristic change in the scattering intensity analogous to the pattern intensity, so that from the position of the three-dimensional pattern and the temporal Course of the backscatter intensity conclusions about the different physical quantities of the movement (location, speed and direction) of the object are possible. The extent of the light pattern is restricted by shaping the object beam analogously to the imaging of an image with a restricted focus area. The detection is carried out by the wave complex-conjugate to the reference beam, i.e. returning in the reverse direction to the reference beam, which is caused by the reflection of the focal point of the image and its backscattering into the hologram, whereby the backscattered light is analyzed by an intensity measurement and by a clear coding, which by the holographic generated light pattern is generated, leads to an assignment of the addressed image area, wherein the light source is used for detection. Method for combining the after Claim 1 built-up holograms with other holograms, characterized in that the holograms are either recorded in the same medium or mounted firmly connected and the one or more holograms serve the purpose of three-dimensional representation and / or optical guidance. Procedure for combining the procedures according to Claim 1 and 2 characterized in that many such areas are combined in one or more holograms and one or more reference beams in order to be able to analyze movement data from many different individual areas or to be able to analyze different combinations of such areas. Procedure according to Claim 1 - 3 characterized in that the reference beam is additionally modulated in time or space. Procedure according to Claim 1 - 4th characterized in that the object movement required for detection relative to the structures described can be omitted in that a movement of the light pattern is effected by suitable measures.

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