Ocean Optics ARCoptix ANIR - Manual (Page 11)

1: Introduction
ARC-00000-000-02-0310 3
Figure 1-2
Figure 1- 2 shows the principle of operation of a LGI. Incoming light is reflected back by a series of
fixed and mobile mirrors acting as a grating and generating a diffraction pattern. To obtain the
interferogram one records the modulation of the zero order in function of the motion of the mobile
mirrors. The path difference (or depth of the grating)
x is an important parameter and given by the
distance between the fixed and the mobile mirrors.
Contrary to the Michelson interferometer that splits wave amplitudes at the beamsplitter, the lamellar
grating interferometer divides the wavefront. At the grating, the wavefront is divided such that one
half of the beam is reflected from the front facets (fixed mirrors in Fig. 1 - 2) and one half from the
back facets (mobile mirrors in Fig. 1 - 2). The distance between the two series of mirrors determines
the optical path difference (OPD)
x between the two parts of the wave. The enormous advantage of
this configuration, compared with a Michelson interferometer, is the absence of a beamsplitter.
Indeed, any additional micro-optical component is a limitation in the particular case of micro-sized
spectrometers. In general, this type of spectrometer is used for wavelengths larger than 100
m;
below, the tolerances are too tight for most machine shops.
The ARCoptix ANIR (Near Infrared) Fiber Optic Fourier Transform Spectrometer connects to a
notebook or desktop PC via a USB 2.0 port. It does not require an external power supply. The
ARCoptix ANIR and the electronics share a single housing.
The ARCoptix ANIR can connect via the USB 2.0 port to any PC that uses a Windows XP/Vista
operating system and has spectrometer operating software installed and configured for use with your
ARCoptix ANIR.
An EEPROM memory chip in each ARCoptix ANIR spectrometer contains calibration coefficients,
coefficients, and the serial number unique to each spectrometer. ARCoptix spectrometer operating
software reads these values from the spectrometer.
The ARCoptix ANIR has two input connectors:
 FSMA receptacle that accepts a fiber optic cable with a standard SMA-905 connector
 USB port that connects to a USB host via a standard USB cable