System converts detector pulse rates to photographs of binary scale indicator lights on continuously moving film. The system then scans the film and transfers the data to computer-compatible magnetic tape

Glass, I. S.

Richard, K. F.

English

NASA Technical Reports Server

OSC 
GATE 
DOWN' 
GATE
,,UP,. 
GATE 
SENSE SENSE 
FILM FILM 
LINE LINE
REFRACTOR
DRIVE
STOP OSC 
GAP IN
DROGRESS

GENERATE

RECORD
GAP 
RECORDER
	 TAPE 
RECORDER 
April 1970	 Brief 70-10141 
NASA TECH BRIEF 
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 Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Pulse Rates Recorded by Digital Film Positioner 
FIL
READER
SENSE 
FILM 
LEVEL 
The problem: 
To record accurately the pulse rates of various 
detected energy impulses (X-ray, infrared; etc.) and 
to convert them to a digital format for use in com-
puter processing. 
The solution: 
A system that first converts detector pulse rates to 
photographs of binary scale indicator lights on con-
AHJD 
tinuously moving film. The resulting record consists 
of parallel trails of dashes and gaps along the film, 
each dash and 'gap being inversely proportional to 
the time required to accumulate the preset number of 
counts set by scaling factors. In order to read and 
digitize the recorded data for computer processing, 
the system scans the film and transfers the data to 
computer-compatible magnetic tape.
(continued overleaf) 
STEP 
FILM 
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 States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19700000135 2020-03-17T00:28:41+00:00Z
How it's done: 
Mechanically, the system operates in the follow-
ing manner. Film (35 mm has been used in a proto-
type) is drawn through a projection gate at the rate of 
70 steps per sec, each step being 3/400 in. or 0.0 19 cm. 
Energy from a light source is concentrated by a con-
denser to project the film image through a lens to the 
back of a light-tight box. A photodiode in the center 
of a small screen can be controlled up or down so that 
the image of a selected trail of dashes and gaps falls 
on it. Output of the diode is fed to a digital incre-
mental tape recorder driven synchronously with the 
film transport. When the trail is black (dash), a zero 
(0) is recorded; when clear, a one (1) is recorded. 
Vertical and horizontal parity check bits are -gen-
erated within the recorder. Physical record gaps are 
generated after each set of 768 characters if the sys-
tem is so commanded. 
To counteract vertical motion of the image, due to 
slight lateral movement of the film, an image stabili-
zation system has been devised. A fiducial light on the 
original data panel is photographed continuously. 
The projected dark image of this light falls across 
two additional sense diodes. If either of these receives 
a signal above a predetermined intensity threshold, 
it causes a stepping motor to rotate a lucite refractor 
that moves the imagç up or down in a compensating 
manner. In this way, the image impingement on the 
sensing photodiode is held constant. 
Operation of the electronic logic circuitry is illus-
trated in the block diagram. A 70 Hz free-running 
oscillator supplies timing pulses to all circuits through 
a gate. With the scaler reset to zero, a manual start 
command causes oscillator pulses to enter the scaler, 
one terminal of the record -"one" gate, the recorder 
advance driver, the film advance driver, and the 
image hunt circuits. As the film reader and the re-
corder step with the drive pulses, the sense diode,
through a Schmitt trigger, opens and closes the record 
"one" gate. This causes "ones" or "zeros" to be 
entered on the magnetic tape. This sequence con-
tinues uninterrupted until the scaler overflows at 768 
counts, at which time a univibrator is triggered, tem-
porarily closing the oscillator gate. A record gap is 
generated by the recorder at this time. When one of 
the fiducial sense diodes (sense film line) detects a 
signal above a certain thfeshold, oscillator pulses 
are fed to the refractor drive through either the "up" 
gate or the "down" gate, and the trail image is thus 
held on the photodiode. 
Notes: 
1. Although no attempt has been made to record 
more than one trail at a time, since the films to be 
digitized are made on several instruments and have 
dissimilar spacings, it is evident that the system 
could be readily expanded to record six trails at 
one time. 
2. In recent experiments, 35 mm film has been digi-
tized to magnetic tape from as many as 62 parallel 
trails.	 - 
3. Requests for fuithèr information may be directed 
to:
Techtology Utilization Officer 
NASA Headquarters 
Washington, D.C. 20546 
Reference: B70-10141 
Patent status: 
Inquiries about- obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: I. S. Glass and K. F. Richard of 
Massachusetts Institute of Technology• 
under contract to 
NASA Headquarters 
(HQN- 10358)
. 
[1 
Brief 70-10141	 - Category 01


Pulse rates recorded by digital film positioner

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