Reflection Confocal Reading

In transmission confocal microscopes that are equipped with phasereading systems, the focus deviates from the pinhole because of the inhomogeneity of the refractive index and/or the thickness of the memory medium and substrate. As a result, the detected signal has a background owing to the local inhomogeneity of the medium and substrate. 

The use of RCM alleviates the problems encountered when the transmission microscope is used, because the beam that is reflected at the data bit arrives at the pinhole even in the presence of inhomogeneity. RCMs, however, have not been used for reading 3D-stored data, primarily because the 3D spatial-frequency band of the reading optics of this configuration does not necessarily pick up the 3D band of the writing optics involved. 

17 Experimental comparison of data reading by (a) the RCM and (b) the transmission microscope. 

18 Band of the writing optics for two-photon processes, and the band of the reading optics for RCM. 

5 Reflection Confocal Reading with Multilayered Medium 

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Figure 16.10 shows readout images of written bits in 26 consecutive layers. The bit and layer intervals were 2 fim and 5 /xm, respectively. The data were read out with a reflection confocal microscope (RCM). The details of the readout system are discussed in the Section 4. With the RCM, the written data are clearly read without crosstalk. 

FIG. 16.10 Readout of bit patterits written into photochromic memory using a diaryiethene derivative.The data were read out with a reflection confocal microscope." ... 

The spatial distribution shown in Figure 16.19b easily has overlapping areas with the CTF, if we carefully select the thickness of the recording layer. As a conclusion, it is possible to read the data with the reflection confocal... 

Figure 16.15 shows the readout result of the four-layered optical memory. The readout system was a reflection-type confocal microscope. For reading, a He-Ne laser was used as a light source, because the urethane-urea copolymer has little absorption for red light. The scattered light at the recorded bit data... 

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