Composer converts binary data to optical form for storage as hologram. Device consists of an array of deformable metal membranes controlled by MOSFET's. Device is fast, produces high contrast ratios, does not degrade with extended use, and can be addressed from diverse angles

Bailey, G. A.

Cosentino, L. S.

English

NASA Technical Reports Server

xl
Output Drain 
Electrode 
(16 in all on 
this block) 
X2 
X3 
X4
Four-MOSFET 
Integrated 
Circuit 
X's and V's
Are Data-Input
Leads Vi	 Vz	 V3	 V4 
August 1975	 B75-10161 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Page Composer to Translate Binary Electrical Data to Optical Form 
.
One of the current research areas in computer 
equipment is the development of optical memories. A 
laser hologram is used to read data into or out of an 
optical storage medium. Such a system requires a 
"page composer" to convert binary data, stored or 
input in electrical form, to an optical form 
(modification of the laser object beam). The data can 
then be stored as a hologram. Liquid crystals, 
electro-optic crystals, and ferroelectric ceramics have 
been used to modulate the laser beam. 
A new page composer has been developed 
consisting of an array of deformable metal mem-
branes controlled by MOSFET's. This device is fast, 
produces high contrast ratios, does not degrade with 
extended use, and can be addressed from diverse 
angles: a combination of features not offered by any 
existing page composers. 
A 4-by-4 array page composer is shown in Figure 1. 
A thin metallic film is mounted on a spacer attached 
to a substrate. There is an electrode in each hole in the 
spacer. Thus each hole is a capacitor in which a 
charge may be stored. If a charge is stored in a 
particular hole, the metal film over that hole will be 
deformed. When the object beam of a laser is directed 
Deformation 
Areas 
Capacitor Metallic 
Hole 
Spacer	 %
,...._strate 
ctor 
Electrode Feedthrough 
Conductor
Figure 1. A Page Composer Block
Figure 2. Underside of Page Composer 
to the array, light striking the deformed portion of the 
surface is scattered. The remaining light is reflected to 
the holographic storage memory. 
Individual capacitors on the page composer are 
charged' by selectively energizing MOSFET's on the 
back of the substrate. The output drain electrode of 
each MOSFET is connected to a feedthrough 
conductor that ends at the electrode in the capacitor. 
Figure 2 shows the underside of the composer. 
There are four integrated circuit chips on the back 
of the composer; each contains four MOSFET's. A 
particular MOSFET is made conductive when it is at 
the intersection of an energized X and an energized Y 
lead. An energized MOSFET causes the film to be 
deformed and a "0" to be written into the optical 
memory for that position. 
A potential of about 30 V is sufficient to deform the 
membrane. Each capacitor-hole diameter is about 2.5 
mm (10 mils), and the spacer is about 0.00125 mm 
(1.25 tim) thick. The substrate may be made from a 
glass or a ceramic, that is coated with a photoresist. 
The substrate is exposed according to the desired 
pattern; then holes are etched through it and filled 
with a conductive material. The electrodes may be 
deposited bya chrome flash followed by about 7 gm of 
aluminum. The unwanted material is etched away by 
a photolithographic process.
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United Slates 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United Slates 	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19750000161 2020-03-19T20:25:55+00:00Z
The spacer is made next, from either SiO or a metal 
such as aluminum. It is made by the same photo-
lithographic steps as the substrate. To make the metal 
membrane, a photoresist layer is deposited over the 
substrate and spacer, filling all the holes in the spacer 
and covering it. The result is dried and polished until 
the spacer is visible. Next, micrometer-size holes are 
made in the spacer to allow the solvent to remove the 
interior photoresist in the final steps. To form the 
holes, a thin film of gelatin is deposited over the chip, 
and a suspension of ZnS particles in water is poured 
over the gelatin layer and allowed to settle. Flashes of 
aluminum (0.06 pm) and then nickel (0.08 m) are 
evaporated over the gel. The chip is subsequently 
wiped off with a wet tissue and rinsed. This removes 
the ZnS particles and leaves a metal film with 
micrometer-size holes where the particles were. This 
film is used as a seeding layer on which the full 
thickness of a nickel membrane is deposited. The 
final step is to remove the photoresist beneath the 
membrane by immersing the array in a dish of 
solvent.
Note: 
Requests for further information may be directed 
Technology Utilization Officer 
Marshall Space Flight Center 
Code ATOI 
Marshall Space Flight Center, Alabama 35812 
Reference: B75-10161 
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
Marshall Space Flight Center 
Code CCO1 
Marshall Space Flight Center, Alabama 35812 
Source: G. A. Bailey
Marshall Space Flight Center and 
L. S. Cosentino of
RCA Corp.
under contract to

Marshall Space Flight Center

(MFS-23173 and MFS-22589)
. 
Categories: 02 (Electronics Systems) 
09 (Mathematics and 
Information Sciences) 
B75-10161
	 03 (Physical Sciences)


Page composer to translate binary electrical data to optical form

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