Aukje Kastelijn

Optical card with parallel readout: proposal for a new robust storage solution

We present a new storage system that combines the advantages of solid state and optical storage for content distribution: a removable, replicable data carrier (optical card) combined with a compact reader with robust mechanics. The system basically consists of a laser light source, a scanner, an optical card and a detector. The bits on the card are represented by transparent and non-transparent areas. The detector is an image sensor enabling parallel read-out of multiple bits. In order to overcome the minimum size of a detector pixel (and multiplex more bits onto one pixel) we illuminate the medium by multiple small optical spots generated by the Talbot effect. This array of optical probes selects a specific segment of bits. The image sensor detects the selected bits from the card. By moving the optical probes the entire card can be read. We present a basic demonstration of the concept.

Optical Read-Only-Memory Card System Based on the Talbot Effect

We present our progress in developing an optical storage system for portable devices, consisting of a removable read-only-memory (ROM) card and a robust reader. The bit patterns stored on the card medium are read out using an array of probes that are generated by means of the Talbot effect. The data are recovered in a parallel fashion by detection with a standard pixelated image sensor. To attain a large data capacity, a multiplexing scheme has been developed: from a large number of different data pages, individual pages can be selected by scanning the probe array over the medium in x and y direction. In order to position the probes accurately it is required to have accurate position information. A method has been devised to generate servo signals by making use of the moire interference effect. A compact demonstrator was built that demonstrates feasibility of this position control method.

Elimination of Jitter in Microlens illuminated Optical Probe Array Using a Filtering Layer for the Optical Read Only Memory Card System

To increase the optical efficiency and areal density of optical read only memory (ROM) card system, a microlens array for generating optical probes by Talbot effects was suggested instead of the aperture array in the previous system. In the microlens array, however, the light from the corner of lens elements can cause the jitter in the optical probes. To eliminate this jitter, a filtering layer is suggested for filtering the light from the corner of lenses. To determine the opening size of filtering layer, the effect of opening size on the jitter and alignment tolerance were examined, which results in the optimum size of 10 µm. The microlens array was integrated on the filtering layer by a UV-molding process. Finally, the elimination of jitter was verified by comparing the beam intensity distributions at the Talbot plane generated by only microlens array and microlens array with filtering layer.

Design and Fabrication of Microlens Illuminated Aperture Array for Optical ROM Card System

In the present study, a microlens illuminated aperture array for optical ROM card system was designed and fabricated using monolithic lithography integration method. Microlens array placed on the array was designed to increase the intensity of light passing the array of apertures with a diameter of 1μm and a period of 15μm. And then Microlens array was fabricated using UV molding as a mean of monolithic lithography integration on aluminum aperture array fabricated using photolithography and reactive ion etching process. Optical properties of the generated optical probes at Talbot distance from aperture array and microlens illuminated aperture array array were measured and compared. The maximum intensity of optical probes of microlens illuminated aperture array increased about 12 times of that of aperture array.

The T-ROM Optical Card System: Content Distribution for Portable Applications

We present an overview of the current development status of the T-ROM optical card system. Special attention is given to the efficient generation of the high quality optical spot array and the integrated piezo actuator.