Patent Description:
The applicant of the present invention has developed data carriers for long-term storage of information based on ceramic materials (see, e.g., <CIT>). These data carriers may utilize a transparent ceramic material as described, e.g., in co-pending application <CIT>.

Moreover, the applicant has been able to substantially increase the data storage density by utilizing various encoding techniques disclosed, e.g., in co-pending applications <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

While the tiny structures of the encoded data may be decoded or read out using techniques such as structured illumination microscopy (SIM) or saturated structured illumination microscopy (SSIM), those techniques will typically allow for visualizing or imaging only a small fraction of the entire data carrier at a time. This makes it difficult to, e.g., quickly access the right subsection of the data carrier or to maneuver between different sections of the data carrier during the read out process.

It is thus an object of the present invention to provide methods and devices for high-speed reading out information from an at least partially transparent data carrier which, at least partially, address these issues.

<CIT> is a comparative prior art document. This object is achieved with a method according to claim <NUM>.

In essence, the present invention is based on the idea to utilize two different imaging techniques to generate a high resolution focus view of a subsection of the data carrier using, e.g., the techniques discussed above, on the one hand and a wide angle overview over a much larger section of the data carrier using, e.g., less advanced imaging techniques. Thus, a much larger portion of the data carrier may be imaged and, e.g., displayed while at the same time the relevant subsection is imaged and, e.g., displayed with a sufficiently high resolution to actually decode the data or display the data with sufficient accuracy.

While the at least partially transparent data carrier preferably is one of the ceramic data carriers disclosed in the applications mentioned above, the method of the present invention is generally suitable for any partially transparent data carrier which allows for imaging in both reflection mode and transmission mode. In other words, the encoded information should provide sufficient contrast in both reflection mode and transmission mode. For example, the information may be encoded by different portions of the data carrier being transparent and non-transparent. The non-transparent portions may be reflecting, absorbing or scattering light. Of course, the property of transparency need only be present for a certain wavelength or a certain wavelength range which is used for illumination.

Accordingly, illumination may take place using any known light source, with the wavelength spectrum of the light source being adapted to the partial transparency of the data carrier. It is particularly preferable to utilize a laser or LEDs for illuminating.

Imaging the at least partially transparent data carrier from the first and second sides in reflection and transmission modes, respectively, may be performed using any known imaging technique. However, in light of the fact that the present invention aims at reading out extremely small structures being possibly even smaller than the wavelength of the illuminating light, it is particularly preferable that imaging the at least partially transparent data carrier from the first side in reflection mode through the high numerical aperture objective utilizes structured illumination microscopy (SIM) or saturated structured illumination microscopy (SSIM). These techniques are known to the skilled person and may be employed in the context of the present invention without difficulties as the combination of the high resolution image with the wide angle image does not have any impact on the way how the high resolution image is taken or generated.

In order to further improve the resolution of the combined image, it is preferred that imaging the at least partially transparent data carrier from a second, opposite side in transmission mode through the low numerical aperture objective utilizes Fourier ptychography. This technique is also well-known and allows for achieving rather high resolution wide angle images by combining various images with the sample being illuminated from different angles in Fourier space.

The low numerical aperture objective has a numerical aperture of less than <NUM>, more preferably less than <NUM> and most preferably less than <NUM>. The high numerical aperture objective has a numerical aperture of at least <NUM>, more preferably at least <NUM> and most preferably at least <NUM>.

The subsection of the image having a higher resolution is preferably arranged in the center of the image.

Preferably, the resolution of the subsection of the image is by at least a factor of <NUM>, more preferably <NUM>, most preferably <NUM> greater than the resolution of the rest of the image. Preferably, the ratio between the area of the entire image and the area of the subsection of the image is at least <NUM>, more preferably at least <NUM>, most preferably at least <NUM>.

The at least partially transparent data carrier is illuminated by means of a digital micromirror device (DMD). The use of such a DMD, for example, allows for creating certain illumination patterns required for SIM, SSIM or Fourier ptychography.

As mentioned above, the inventive method is suitable for any at least partially transparent data carrier. The present invention utilizes a data carrier comprising a ceramic substrate and a ceramic coating layer, wherein the material of this ceramic substrate is different from the material of the coating layer. Preferably, the coating layer has a thickness no greater than <NUM>, more preferably no greater than <NUM>, even more preferably no greater than <NUM> and most preferably no greater than <NUM>. Preferably, the thickness of the ceramic substrate is at most <NUM>, preferably at most <NUM>, more preferably at most <NUM>, most preferably at most <NUM>. Preferably, the ceramic substrate comprises at least <NUM>%, more preferably at least <NUM>%, by weight of one or a combination of: a metal oxide such as Al<NUM>O<NUM>, TiO<NUM>, SiO<NUM>, ZrO<NUM>, ThO<NUM>, MgO, Cr<NUM>O<NUM>, Zr<NUM>O<NUM>, V<NUM>O<NUM>; a metal nitride such as CrN, CrAlN, TiN, TiCN, TiAlN, ZrN, AlN, VN, Si3N4, ThN, HfN, BN; a metal carbide such as TiC, CrC, Al<NUM>C<NUM>, VC, ZrC, HfC, ThC, B4C, SiC; a metal boride such as TiB<NUM>, ZrB<NUM>, CrB<NUM>, VB<NUM>, , SiB<NUM> ,ThB<NUM>, HfB<NUM> , WB<NUM>, WB<NUM>; and a metal silicide such as TiSi<NUM>, ZrSi<NUM>, MoSi<NUM>, WSi<NUM>, PtSi, Mg<NUM>Si. Preferably, the coating layer comprises at least one of: a metal nitride such as CrN, CrAlN, TiN, TiCN, TiAlN, ZrN, AlN, VN, Si<NUM>N<NUM>, ThN, HfN, BN; a metal carbide such as TiC, CrC, Al<NUM>C<NUM>, VC, ZrC, HfC, ThC, B<NUM>C, SiC; a metal oxide such as Al<NUM>O<NUM>, TiO<NUM>, SiO<NUM>, ZrO<NUM>, ThO<NUM>, MgO, Cr<NUM>O<NUM>, Zr<NUM>O<NUM>, V<NUM>O<NUM>; a metal boride such as TiB<NUM>, ZrB<NUM>, CrB<NUM>, VB<NUM>, SiB<NUM> ,ThB<NUM>, HfB<NUM>, WB<NUM>, WB<NUM>; or a metal silicide such as TiSi<NUM>, ZrSi<NUM>, MoSi<NUM>, WSi<NUM>, PtSi,, Mg<NUM>Si. Preferably, the ceramic substrate is transparent to the wavelength of the illuminating light. Preferably, the ceramic substrate comprises a glassy transparent ceramic material or a crystalline ceramic material and/or the ceramic substrate comprises one or a combination of: sapphire (Al<NUM>O<NUM>), silica (SiO<NUM>), zirconium silicate (Zr(SiO<NUM>)), zirconium dioxide (ZrO<NUM>).

The ceramics based data carriers mentioned above and methods of manufacturing the same are described in more detail in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

The present invention further relates to a device for high-speed reading out information from an at least partially transparent data carrier. The device comprises a substrate holder for mounting an at least partially transparent data carrier; a high numerical aperture objective on a first side of the substrate holder; a low numerical aperture objective on a second, opposite side of the substrate holder; a light source for illuminating an at least partially transparent data carrier mounted on the substrate holder from the first side through the high numerical aperture objective; a first image detector for imaging the at least partially transparent data carrier from the first side in reflection mode through the high numerical aperture objective in order to generate focus view data; a second image detector for imaging the at least partially transparent data carrier from the second side in transmission mode through the low numerical aperture objective in order to generate wide angle data; and a central processing unit adapted and arranged for combining the focus view data and the wide angle data received from the first and second image detectors in order to generate an image comprising a wide angle view of at least a section of the data carrier with a subsection of said image having a higher resolution than the rest of the image.

Of course, all features discussed above with respect to the inventive method may be analogously employed in the context of the inventive device.

Preferably, a spatial light modulator (SLM) is arranged between the light source and the high numerical aperture objective.

The first and second image detectors may, e.g., be CCD cameras adapted for capturing light in the wavelength range of illumination.

The present invention will now be further illustrated with reference to the figures, which show:.

<FIG> schematically shows an example of an optical setup for imaging an at least partially transparent data carrier <NUM> mounted on a substrate holder <NUM> in reflection mode in order to generate focus view data <NUM>. The at least partially transparent data carrier <NUM> is illuminated from a first side (here: a top side) through a high numerical aperture objective <NUM> by means of an LED <NUM> and a digital micromirror device <NUM>. Of course, another light source may be utilized and the digital micromirror device is not necessarily required for generating focus view data. Moreover, a spatial light modulator may be utilized instead of the DMD <NUM>. Light being reflected or scattered by the data carrier <NUM> can be imaged from the first side (here: the top side) in reflection mode through the same high numerical aperture objective <NUM> by means of, e.g., a CCD camera <NUM> and a semi-transparent mirror <NUM>. This imaging technique generates focus view data <NUM> schematically illustrated at the bottom of <FIG>. The exemplary focus view data <NUM> shown in <FIG> have been generated by an Olympus BX <NUM> with 100x microscope objective with an NA of <NUM>. The sample shown is a ceramic material comprising circular recesses generated by laser pulses.

<FIG> schematically shows an example of an optical setup for generating wide angle data <NUM>. The data carrier <NUM> being mounted on the substrate holder <NUM> is again illuminated from a first side (here: the top side) through the high numerical aperture objective <NUM> by means of an LED <NUM>, DMD <NUM> and the semi-transparent mirror <NUM> (which would not be required for this part of the setup). However, contrary to <FIG>, in case of <FIG> imaging is performed from a second, opposite side (here: the bottom side) in transmission mode through a low numerical aperture objective <NUM> in order to generate wide angle data <NUM>. Again, a CCD camera <NUM> or any other image detector may be utilized for imaging. The wide angle data shown at the bottom of <FIG> have been taken from the sample discussed above, utilizing an Olympus BX <NUM> with 10x microscope objective with an NA of <NUM>.

According to the present invention the optical setups shown in <FIG> are combined in a single device for high-speed reading out information from the at least partially transparent data carrier <NUM>. This is exemplary shown in <FIG>, where all components of <FIG> have been combined accordingly. The setup allows for imaging the data carrier <NUM> from the first (top) side in reflection mode in order to generate focus view data and for imaging the data carrier <NUM> from a second, opposite (bottom) side in transmission mode in order to generate wide angle data. For both imaging steps, illumination can take place from the first, top side through the high numerical aperture objective <NUM>.

While a very simple setup with only two CCD cameras <NUM> and <NUM> for imaging is shown in <FIG>, it will be evident from the above discussion that either or both of the imaging components of the setup may be more elaborate utilizing, for example, SIM, SSIM and/or Fourier ptychography. For this purpose, the DMD <NUM> may generate specific illumination patterns required for those imaging techniques and an additional processing unit may be required in order to control the DMD <NUM> as well as the CCD cameras <NUM> and <NUM>.

Of course, the setup shown in <FIG> may not only be used for reading out data from the data carrier <NUM>, but could also be utilized for encoding data on the data carrier <NUM> using an additional laser <NUM>. The encoding process has been described in detail in the above-mentioned patent applications and need not be further elucidated here.

The inventive method utilizing the above-discussed setup is schematically depicted in <FIG> which, on the left side, again shows the optical setup of <FIG> with an additional central processing unit (CPU) <NUM> being shown in the centre of <FIG>. Said CPU <NUM> recieves the focus view data <NUM> from the CCD camera <NUM> as well as the wide angle data <NUM> from the CCD camera <NUM> and combines the data in order to generate an image <NUM> schematically depicted on the right side of <FIG>. Said image <NUM> comprises a wide angle view <NUM> of at least a section of the data carrier <NUM> with a subsection <NUM> of said image having a higher resolution than the rest of the image. Of course, neither the image <NUM> nor the subsection <NUM> need be circular as shown in <FIG>, but could also be rectangular, quadratic or of any other shape. It is, however, preferred that the subsection <NUM> of the image <NUM> is arranged in the center of the image <NUM> as shown in <FIG>.

Claim 1:
A method for high-speed reading out information from an at least partially transparent data carrier (<NUM>), the method comprising the steps of:
illuminating an at least partially transparent data carrier (<NUM>) from a first side through a high numerical aperture objective (<NUM>) having a numerical aperture of at least <NUM>,
wherein the data carrier comprises a ceramic substrate and a ceramic coating layer, wherein the material of the substrate is different from the material of the coating layer;
imaging the at least partially transparent data carrier (<NUM>) from the first side in reflection mode through the high numerical aperture objective (<NUM>) in order to generate focus view data (<NUM>);
imaging the at least partially transparent data carrier (<NUM>) from a second, opposite side in transmission mode through a low numerical aperture objective (<NUM>) having a numerical aperture of less than <NUM> in order to generate wide angle data (<NUM>); and
combining the focus view data (<NUM>) and the wide angle data (<NUM>) in order to generate an image (<NUM>) comprising a wide angle view of at least a section of the data carrier with a subsection of said image having a higher resolution than the rest of the image.