Browse Prior Art Database

Bar Code Scan Head for Reading Etched Marks on Metallic Surfaces

IP.com Disclosure Number: IPCOM000060054D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Juliana, A: AUTHOR [+2]

Abstract

A considerable improvement in signal-to-noise ratio can be achieved by using the system shown in the figure. A HeNe laser is used as the light source (alternative lasers or LEDs (light-emitting diodes) at other wavelengths could be used). A focusing lens is used to produce a focused spot size which is smaller than the bar width on the edge of the metal surface. Due to machined turning marks on the edge of the metal surface, light is diffracted along a line parallel to the axis of rotation of the metal surface. A cylindrical lens is then used to collect the diffracted light and image it onto the photodetector. A mask may be placed in front of the lens to restrict the collection solid angle to only that of the diffracted light from the turning marks.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Bar Code Scan Head for Reading Etched Marks on Metallic Surfaces

A considerable improvement in signal-to-noise ratio can be achieved by using the system shown in the figure. A HeNe laser is used as the light source (alternative lasers or LEDs (light-emitting diodes) at other wavelengths could be used). A focusing lens is used to produce a focused spot size which is smaller than the bar width on the edge of the metal surface. Due to machined turning marks on the edge of the metal surface, light is diffracted along a line parallel to the axis of rotation of the metal surface. A cylindrical lens is then used to collect the diffracted light and image it onto the photodetector. A mask may be placed in front of the lens to restrict the collection solid angle to only that of the diffracted light from the turning marks. When the beam strikes an etched bar, light is scattered over a large solid angle (approaching 2 Pi steradians). Thus, a large signal difference is observed due to the large difference in solid angle between light diffracted from the turning marks and light scattered from the etched bars. With an f/5 cylindrical collection system this ratio was found to be 25:1.

1

Page 2 of 2

2

[This page contains 3 pictures or other non-text objects]