Two different laser-scanning methods may be utilized. In each case scanned cylindrical bullet surface is displayed ""unwrapped'' on oscilloscope screen. Bullets are compared by photographing each display and superimposing negatives of two images. With some modifications bullets can be scanned and compared by superimposing images on screen of dual-beam oscilloscope

Nakich, R. B.

Woodburgy, R. C.

English

NASA Technical Reports Server

. ^Sine-Wave 
Mirror
Phase 
I	 Shifter
Condensing
Lens
Condensing I
Lens
Bullet 
Sawtooth 
Generator 
Motor C 
Motor 
Speed	
Phase-Shift Adjuster Control
DC 
Voltage 
115 Vac
I
Matching	 I 
TransformerI 
Video
 
Amplifier 
)Photomultiplier 
Oscilloscope 
OZ
0 
Display 
OH 
I 
Helium-	
•Q - - - - Neon Laser
Diverging 
Lens
August 1974	 B74-10102 
NASA TECH BRIEF 
NASA Pasadena Office
	
£ 
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. 
Laser-Scanning Techniques for Rapid Ballistics Identification 
The problem: 
Firearms involved in a crime are identified by 
standard ballistics tests. In this procedure, a test 
bullet fired in the laboratory is compared to the one 
under investigation to see if their markings are identical. 
Since every rifled bore has unique irregularities, bullets 
fired from the same gun will have the same marks. The 
markings are compared with a microscope. This method 
normally takes from half hour to as long as several hours 
and results in significant findings only 70 percent of 
the time.
The solution: 
Bullets are compared faster and more accurately using 
either one of two newly-developed laser techniques. 
How it's done: 
The apparatus used is very similar in both methods 
except different laser-scanning methods are utilized. 
In each case the scanned cylindrical bullet surface is 
displayed "unwrapped" on an oscilloscope screen. Two 
bullets are compared by photographing each display 
and superimposing the negatives of the two images. 
Laser Scanning Apparatus
(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 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=19740000102 2020-03-17T14:04:45+00:00Z
With some modifications in the apparatus, two bullets 	 Notes: 
can be scanned and comnared by superimposing their	 1. Both 
images on the screen of a dual-beam oscilloscope. 
The apparatus, in which an electric motor is used to 
rotate a bullet through a single laser scan, is illustrated in 
the figure. A helium-neon laser beam that is expanded 
through the diverging lens and condensed by the other 
two lenses illuminates the surface of the bullet. The 
laser beam is deflected horizontally by a piezoelectrically 
driven mirror at a 2-kHz rate controlled by a sine-wave 
oscillator. The oscillator signal is also fed into the 
horizontal sweep terminal of the oscilloscope. 
The bullet is rotated by an ac motor. The rotating 
shaft of the motor is coupled to a sawtooth waveform 
generator, which includes a phase-shifting network to 
synchronize the horizontal laser sweep with the oscillo-
scope scan. The sawtooth generator produces one 
sawtooth signal for each motor shaft rotation. 
The scattered laser beam from the bullet surface is 
collected by a photomultiplier, which feeds video 
signals through a video amplifier into the oscilloscope. 
The scanned bullet surface is displayed on a storage-
type cathode-ray-tube (CRT) screen. 
A similar display is obtained in a raster scan arrange-
ment. The apparatus is similar to the one described 
except that the bullet is not rotated. Instead it is 
scanned using two piezoelectrically driven mirrors, one 
driven horizontally at 2 kHz and the other driven 
vertically at 50 Hz.
firearm identification methods may be of 
interest to law enforcement agencies. 
Requests for further information may be directed to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP74-10 102 
Patent status:	 - 
This invention has been patented by NASA (U.S. 
Patent No. 3,800,074). Inquiries concerning nonex-
clusive or exclusive license for its commercial develop-
ment should be addressed to: 
Patent Counsel 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: Raymond C. Woodbury of
Caltech/JPL and

Robert B. Nakich of 
Time Zero Corp.
both under contract to
NASA Pasadena Office 
(NPO-1 1861) [I: 
B74-10102	 Category 03, 02


Laser-scanning techniques for rapid ballistics identification

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