Variable thickness double-refracting plate

Patent · Thu Jan 01 00:00:00 EST 1976

OSTI ID:862538

Hadeishi, Tetsuo ^[1]

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1. Berkeley, CA

This invention provides an A.C., cyclic, current-controlled, phase retardation plate that uses a magnetic clamp to produce stress birefringence. It was developed for an Isotope-Zeeman Atomic Absorption Spectrometer that uses polarization modulation to effect automatic background correction in atomic absorption trace-element measurements. To this end, the phase retardation plate of the invention is a variable thickness, photoelastic, double-refracting plate that is alternately stressed and released by the magnetic clamp selectively to modulate specific components selected from the group consisting of circularly and plane polarized Zeeman components that are produced in a dc magnetic field so that they correspond respectively to Zeeman reference and transmission-probe absorption components. The polarization modulation changes the phase of these polarized Zeeman components, designated as .sigma. reference and .pi. absorption components, so that every half cycle the components change from a transmission mode to a mode in which the .pi. component is blocked and the .sigma. components are transmitted. Thus, the Zeeman absorption component, which corresponds in amplitude to the amount of the trace element to be measured in a sample, is alternately transmitted and blocked by a linear polarizer, while the circularly polarized reference components are continuously transmitted thereby. The result is a sinusoidally varying output light amplitude whose average corresponds to the amount of the trace element present in the sample.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• DOE Contract Number: W-7405-ENG-48
• Assignee: United States of America as represented by United States Energy (Washington, DC)
• Patent Number(s): US 3957375
• OSTI ID: 862538
• Country of Publication: United States
• Language: English

Related Subjects

variable
thickness
double-refracting
plate
provides
cyclic
current-controlled
phase
retardation
magnetic
clamp
produce
stress
birefringence
developed
isotope-zeeman
atomic
absorption
spectrometer
polarization
modulation
effect
automatic
background
correction
trace-element
measurements
photoelastic
alternately
stressed
released
selectively
modulate
specific
components
selected
consisting
circularly
plane
polarized
zeeman
produced
dc
field
correspond
respectively
reference
transmission-probe
changes
designated
sigma
half
cycle
change
transmission
mode
component
blocked
transmitted
corresponds
amplitude
amount
trace
element
measured
sample
linear
polarizer
continuously
result
sinusoidally
varying
output
light
average
output light
atomic absorption
trace element
magnetic field
variable thickness
circularly polarized
dc magnet
transmission mode
circularly polarize
absorption spectrometer
/356/359/