Photorefractive read-only optical memory apparatus using phase, frequency, and angular modulation

• US 6,026,053 A
• Filed: 05/21/1999
• Issued: 02/15/2000
• Est. Priority Date: 05/21/1999
• Status: Expired due to Fees

• Current Assignee: The Government Of The United States As Represented By Director Natural Security Agency
• Original Assignee: The United States of America As Represented By The Director National Security Agency
• Inventors: Satorius, Duane Anthony
• Primary Examiner(s): LE, VU ANH
• Application Number:
  US09/316,031
• Time in Patent Office: 270 Days
• Field of Search: 365/235, 365/234, 365/120, 365/127
• US Class Current: 365/235
• CPC Class Codes: G11C 13/04 using optical elements ; using other beam accessed elements, e.g. electron or ion beam

Abstract

The present invention stores and retrieves digital information by altering the phase transmission characteristics of a multiple layer phase recording by modulating the carrier frequency and the carrier frequency angle. These layers are organized into several regions, called page areas, which contain an array of juxtaposed encoded digital information data. Each page area may have several pages of digital information; each recorded with a different carrier frequency and carrier angle. The data layers are stacked together and aligned such that the page areas and encoded digital information on them are also aligned with each other into books. When one of these books is selectively illuminated by a controllable light source, a lenslet aligned with that book projects the transformed images of the data pages within that book, through a shutter array, and a reimaging lens onto a photosensor detector array. By selectively illuminating individual books and selectively opening the transform plane shutter to pass a single desired transformed page of digital data, any desired page of any desired book in the stack of data layers can be imaged onto the photosensor detector array. Pages of data can thus be randomly accessed and all data on that page can be read in parallel at speeds limited only by the access speeds of the illumination source, spatial frequency plane shutter array, and photosensor detector array.

Claims

1. A photorefractive read-only optical memory apparatus using phase, frequency, and angular modulation, comprising:

a controllable quasi-monochromatic light source for producing collimated light;

at least one photorefractive data layer deployed orthogonally to the direction of propagation of the collimated light of said controllable quasi-monochromatic light source and arranged such that the collimated light is transmitted through said photorefractive data layer and further comprising;

at least one page area for storing recorded information and altering the transmitted collimated light, further comprising;

at least one data page containing an array of phase altering storage pixels for encoding the recorded information as a phase delay of the transmitted collimated light, wherein said array of phase altering storage pixels are aligned, with respect to the transmitted collimated light, with all of said arrays of phase altering storage pixels in the same one of said page areas and with all of said arrays of phase altering storage pixels in any of said page areas aligned, with respect to the transmitted collimated light, with the same one of said page areas, and further wherein all of the phase altering storage pixels in any of said array of phase altering storage pixels in any of said data pages are carrier modulated in frequency and angle such that the carrier frequency and angle is unique for each data page amongst all the data pages aligned, with respect to the transmitted collimated light;

a lenslet for each of said alignment of page areas for accepting the transmitted collimated light after passing through said alignment of page areas and transmitting transformed images of each one of said data pages, in accordance with the unique carrier frequency and angle modulation of said contained array of phase altering storage pixels, onto a spatial frequency plane;

a transform plane shutter array, deployed in the spatial frequency plane, comprising a plurality of shutter elements for selectively passing the transmitted transformed image of only one of said data pages and not transmitting the unmodulated carrier transform;

a reimaging lens for accepting the passed transmitted transformed image of only one of said data pages and imaging the passed transmitted transformed image of only one of said data pages onto an image plane;

a photodetector array deployed in the image plane to receive the transmitted transformed image of only one of said data pages and reproduce the recorded data;

means for controlling said transform plane shutter array to selectively chose one of said data pages; and

means for accepting the reproduced data from said photodetector array.

2. The photorefractive read-only optical memory apparatus using phase, frequency, and angular modulation of claim 1, wherein the encoding of the recorded information in said array of phase altering storage pixel is binary.

3. The photorefractive read-only optical memory apparatus using phase, frequency, and angular modulation of claim 1, wherein the encoding of the recorded information in said array of phase altering storage pixel is recorded at a plurality of levels of phase delay.

4. The photorefractive read-only optical memory apparatus using phase, frequency, and angular modulation of claim 1, wherein said controllable quasi-monochromatic light source can selectively transmit collimated light through only one of said alignment of page areas and further comprising means to control said controllable quasi-monochromatic light source to selectively chose one of said alignment of page areas for light transmission.

5. The photorefractive read-only optical memory apparatus using phase, frequency, and angular modulation of claim 1, wherein said controllable quasi-monochromatic light source can transmit collimated light at a plurality of selected wavelengths.

6. The photorefractive read-only optical memory apparatus using phase, frequency, and angular modulation of claim 1, wherein said photorefractive data layers and said lenslets are bonded together forming a removable and replaceable read-only data media.