Method and Assembly for Confocal, Chromatic, Interferometric and Spectroscopic Scanning of Optical, Multi-Layer Data Memories

• US 20080151253A1
• Filed: 02/03/2006
• Published: 06/26/2008
• Est. Priority Date: 02/03/2005
• Status: Active Grant

• Current Assignee: Universitaet Stuttgart
• Original Assignee: Universitaet Stuttgart
• Inventors: Osten, Wolfgang, Wiesendanger, Tobias, Ruprecht, Aiko, Kohler, Christian, Berger, Reinhard, Droste, Ulrich, Pruss, Christof, Korner, Klaus
• Granted Patent: US 7,876,446 B2
• Time in Patent Office: Days
• US Class Current: 356/451
• CPC Class Codes: G01B 2210/50 Using chromatic effects to achieve wavelength-dependent depth resolution
• CPC Class Codes: G01B 2290/15 Cat eye, i.e. reflection always parallel to incoming beam
• CPC Class Codes: G01B 9/02036 by using chromatic effects, e.g. a wavelength dependent focal point
• CPC Class Codes: G01B 9/02042 Confocal imaging
• CPC Class Codes: G01B 9/02044 Imaging in the frequency domain, e.g. by using a spectrometer
• CPC Class Codes: G01B 9/02057 by using common path configuration, i.e. reference and object path almost entirely overlapping
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 3/0087 with index gradient
• CPC Class Codes: G11B 2007/0013 for carriers having multiple discrete layers
• CPC Class Codes: G11B 7/1275 Two or more lasers having different wavelengths
• CPC Class Codes: G11B 7/13 Optical detectors therefor
• CPC Class Codes: G11B 7/1381 Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops G11B7/1353 - G11B7/1369 take precedence
• CPC Class Codes: G11B 7/1384 Fibre optics
• CPC Class Codes: G11B 7/14 specially adapted to record on, or to reproduce from, more than one track simultaneously
• CPC Class Codes: G11B 7/24038 Multiple laminated recording layers

Abstract

An interferometric confocal method and assembly for terabyte volume optical data memories couples two-beam spectral interferometry to chromatic confocal technology and permits a longitudinal splitting of foci in the memory volume, with the foci having limited diffraction. A spectrometer is located downstream of the interferometer with confocal discrimination in the beam path. A diffractive optical zone lens (DOZE) with a usage of the first diffraction order is introduced into the interferometric beam path to achieve longitudinal chromatic splitting. The interferometer can be a fibre-coupled interferometer with a retroreflector in the fibre-coupled reference arm and with wavelength-dependent optical path difference modification by dispersion or diffraction. The optical path difference in the interferometer is set so that easily detectable wavelets are formed from detectable interferograms by spectral analysis.

Claims

1. An interferometric confocal method for writing to and/or reading from terabyte volume optical data storage devices, using reflected light or transmitted light, comprising at least one multi-wavelength source (1, 1a) of electromagnetic radiation, an interferometer and comprising microscopic imaging of the interior of the volume storage device by means of a focusing system onto a screened receiver (11) of electromagnetic radiation, characterized in that a chromatic confocal microscopic technology method is combined from a method standpoint with a spectral two-beam interferometry, in particular a conventional spectral two beam interferometry, wherein a spectrometer (100) is disposed upstream of the screened receiver (11), and the interferometer works with an optical path difference not equal to zero, and in the case of a reflective region or dot in the storage medium (108), at least one wavelet is generated over the spectral axis of the spectrometer (100).

2. The interferometric confocal method for terabyte volume storage devices, as claimed in claim 1, characterized in that foci are formed by longitudinal chromatic aberration, or chromatic depth splitting, at different depths of the storage medium (108), wherein the spherical aberration is made to a minimum for each focus of any desired wavelength in the spectral range used.

3. The interferometric confocal method for terabyte volume storage devices, as claimed in claim 1, characterized in that logical scanning windows which are formed from the sensor elements of the spectrometer which evaluate a wavelet in each case on the spectrometer axis are electronically tracked, in the read-out operation for wavelets jumping or drifting on the spectral axis, to said wavelets in highly dynamic fashion.

4. The interferometric confocal method for terabyte volume storage devices, as claimed in claim 1, characterized in that the signal amplitude of wavelets is evaluated in order to obtain digital data.

5. The interferometric confocal method for terabyte volume storage devices, as claimed in claim 1, characterized in that in at least one arm of the interferometer, by dispersion and/or diffraction, the optical path difference is made wavelength-dependent in a predetermined manner in order to influence the center frequency of the wavelets.

6. An interferometric confocal assembly for writing and/or reading for terabyte volume optical data storage devices using reflected light or else using transmitted light, comprising an interferometer, and comprising at least one multi-wavelength source (1, 1a) of electromagnetic radiation, and comprising microscopic imaging of the interior of the volume storage device by means of a focusing system, which is arranged in the interferometric beam path, onto a screened receiver (11) of electromagnetic radiation, characterized in that:

the interferometer is coupled to a chromatic confocal assembly in the imaging beam path of the focusing system, a spectrometer (100) is disposed upstream of the screened receiver (11) and no chromatic confocal components are arranged in the reference beam path.

7. The interferometric confocal assembly as claimed in claim 6, wherein the assembly is designed such that the interferometer works with an optical path difference not equal to zero.

8. The interferometric confocal assembly as claimed in claim 6, wherein the arrangement is designed such that in the case of a reflective region or dot in the storage medium, at least one wavelet is generated over the spectral axis of the spectrometer.

9. The interferometric confocal assembly for optical data storage devices, as claimed in claim 6, characterized in that the interferometer is formed as a two-beam interferometer.

10. The interferometric confocal assembly for optical data storage devices, as claimed in claim 6, characterized in that at least one diffractive optical zone lens (5, 55) is arranged in the focusing system.

11. The interferometric confocal assembly for optical data storage devices, as claimed in claim 6, characterized in that the diffractive optical zone lens (5, 55) is arranged in the focusing system'"'"'s pupil situated in the Fourier plane of the focusing objective (6, 12, 12b).

12. The interferometric confocal assembly for optical data storage devices, as claimed in claim 11, characterized in that the interferometer is formed as fiber-coupled interferometer.

13. The interferometric confocal assembly for optical data storage devices, as claimed in claim 11, characterized in that the interferometer is a Linnik interferometer or Mach-Zehnder interferometer.

14. The interferometric confocal assembly for optical data storage devices, as claimed in claim 11, characterized in that the interferometer is formed as a common-path interferometer.

15. The interferometric confocal assembly for optical data storage devices, as claimed in claim 14, characterized in that the interferometer is a Mirau interferometer.

16. The interferometric confocal assembly for optical data storage devices, as claimed in claim 14, characterized in that the interferometer a Fizau interferometer.

17. The interferometric confocal assembly for optical data storage devices, as claimed in claim 8, characterized in that at least one fiber-coupled line spectrometer (10, 11) is disposed downstream of the interferometer.

18. The interferometric confocal assembly for optical data storage devices, as claimed in claim 8, characterized in that a retroreflector is formed such that it can be regulated sensitively in terms of its axial position in the reference beam path of the interferometer in order always to set the optical path difference in the interferometer to be somewhat different from zero with respect to the depth of the layers of a selected packet.

19. The interferometric confocal assembly for optical data storage devices, as claimed in claim 18, characterized in that the retroreflector is a triple-mirror reflector (116).

20. The interferometric confocal assembly for optical data storage devices, as claimed in claim 8, characterized in that at least one optical element is arranged in the reference beam path with dispersive material.

21. The interferometric confocal assembly for optical data storage devices, as claimed in claim 20, characterized in that the optical element with dispersive material in the collimated reference beam path is formed as a plane-parallel plate (117).

22. The interferometric confocal assembly for optical data storage devices, as claimed in claim 19, characterized in that a diffraction module with gratings is arranged in the collimated reference beam path.

23. The interferometric confocal assembly for optical data storage devices, as claimed in claim 22, characterized in that the diffraction module is constructed by means of two or four structurally identical phase gratings (118) which are all arranged parallel to one another.

24. The interferometric confocal assembly for optical data storage devices, as claimed in claim 23, characterized in that the phase gratings (118) are formed at phase-mostly SLMs and are formed such that they can be controlled electronically in terms of their grating parameters.

25. A chromatic confocal assembly for writing for terabyte volume optical data storage devices, using reflected light or using transmitted light, comprising at least one multi-wavelength source (1, 1a) of electromagnetic radiation characterized in that at least one chromatic confocal component is arranged in an imaging beam path of a focusing system of the assembly.

26-28. -28. (canceled)