Noise reduction in volume holographic memories

Details Noise reduction in volume holographic memories Noise reduction in volume holographic memories

1998-05-01

2001-05-01

Chang, Jon (Department: 2623)

Image analysis

Image enhancement or restoration

Artifact removal or suppression

C382S305000, C382S210000, C359S007000, C365S125000

Reexamination Certificate

active

06226415

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of reducing local noise in holographic images stored in volume holographic memories.
2. Related Art
Recent extensive results at various places have shown that holographic memory has a great potential for a future memory with large storage capacity of one trillion bits per cubic centimeters and fast random access of approximately one million pages per second.
However, an image reconstructed from a holographic memory is significantly degraded by various interference fringes originating from dust on optical components, unwanted reflection from various surfaces, etc. As a result, signal-to-noise ratio (SNR) and storage capacity of a holographic memory is greatly reduced, posing a serious bottleneck in the practical use of holographic memory.
Although, there have been approaches suggested to reduce the coherent noise, most of them are either impractically complicated, poor in performance, or time-consuming. Furthermore, most of this previous work did not consider noise from SLMs (Spatial Light Modulators) or CCDs (Charge Couple Devices).
SUMMARY OF THE INVENTION
It is an object of this invention to provide a method for reducing local noise in a holographic memory system.
It is an object of this invention to provide a method for reducing local from the SLM and the CCD in a holographic memory system.
It is yet another object of this invention is to provide an improved method for reducing local noise in a holographic memory system.
The invention according to a preferred embodiment provides a method for reducing local noise in holographic images stored in a holographic memory system by: storing a white reference image and a black reference image in a holographic memory system, storing a series of data images in said memory system, and applying a simple model based on a point-to-point method of linear interpolation to the series of data images, the black reference image and the white reference image to provide a series of corrected data images having reduced noise. The simple model is preferably in the form of
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which has temporal stability for a plurality of data images for each set of the black and white reference images.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.


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Bashaw et al. “Crosstalk Control for Multiplex Holography.” IEEE NLO 1994, pp. 224-226, Jul. 1994.*
Yeh et al. “Hologram Restoration and Enhancement in Photorefractive Media.” IEEE NLO 1994, pp. 421-423, Jul. 1994.

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