ALI V2

ALI V2 is a project developed by Matt Kozun from 2014 to 2018

ALI V2 Optical Design

The optical design was produced using CODE V. The final design file can be found here: \\utls\users\mnk792\!PhD\!Year9Term1\CODE V ALI Model\ALI V2 with close to Brimrose AOTF

Below is an overview of the optical components within the ALIV2 instrument (Note: This does not depict the final design. The elements are however representative of those in the ALI V2 instrument).

The ALIV2 optical layout is divided into 4 primary subsystems:

  • Front end telescope (Elements 3 and 4)
    • The front end telescope is used to map the 6 degree FOV required to capture scattered sunlight from the balloon altitude down to the surface of the earth, into the 4 degrees required by the AOTF. It consists of 2 off-axis parabolic mirrors. Element 3 has a focal length of 50.8 mm and element 4 has a focal length of 76.2 mm. Together they provide an angular magnification of 0.666.
  • AOTF (Element 5)
    • Used for filtering wavelengths from 500 – 1500 nm. More details below.
  • Back End Camera and lens (elements 7-12)
    • The back end system is composed of fold mirrors (elements 7 and 8), a camera lens (elements 9,10 and 11) and finally the detector (element 12). The fold mirrors are in place to provide sufficient separation between the -1st and 0th order light such that no 0th order light should reach the detector plane. The transmissive elements 9-11 form an achromatic triplet made of CaF2, NBK-7 and CaF2 respectively. The spacing between elements 10 and 11 is defined by SM1S01 plastic optics spacers. This doublet is then aligned positioned with respect to element 9 to capture a 4 degree full FOV on the detector plane (along the 640 direction). The detector is an OWL-640 Vis-InGaAs detector that will be described below. It has 640×512 resolution. It is mounted sideways such that the 640 pixel direction captures the horizontal component of the limb.
  • Polarization components (elements 1,2 and 6)
    • The linear polarizers (elements 2 and 6) are necessary to mitigate stray light in ALI. The first polarizer only passes vertically polarized light through the system to the AOTF. When the photon-phonon momentum matching condition is satisfied within the AOTF and diffraction occurs, the polarization state is rotated by 90 degrees, so the filtered wavelengths exit horizontally polarized. The second polarizer is use to only pass this diffracted light, and removes the zeroth order light that did not experience any diffraction. Element 1 in the system is a liquid crystal polarization rotator, which will be discussed further in a following section. It is used to select light that is initially either vertically or horizontally polarized light to enter the AOTF.

ALI Hardware

The SolidWorks model of ALI V2 can be found here:  \\utls\users\mnk792\!PhD\!Year8Term3\Solidworks\ALIV2.SLDASM

The parts list can be found here:

\\utls\users\mnk792\!PhD\!Year8Term3\ALIV2 Parts List

The sales orders located in the folder:  \\utls\users\mnk792\!PhD\Important Documents

The primary sources for parts are:

  • Brimrose Corporation of America (AOTF)
  • Gamble Technologies (Detector)
  • Delta Photonics (Liquid Crystal Polarization Rotator)
  • Thorlabs (Optomechanical hardware, some optics)
  • Edmond Optics (Some optics)
  • Newport Corporation (Optomechanical mounts)
  • Protocase (external and internal cases)

Select Hardware Component Details

Acousto-Optic Tunable Filter

A 10 mm x 10 mm TeO2 dual transducer AOTF is used to filter wavelengths from 500 nm – 1500 nm. The documentation for the AOTF is found here: \\utls\users\mnk792\!PhD\Important Documents\ AOTF Manual

The AOTF is controlled by a DS1 Driver from Brimrose. The documentation for this can be found here:  \\utls\users\mnk792\!PhD\!Year9Term3\ALI V3\Data Sheets\AOTF Driver Document

This driver can be operated by running \\utls\users\mnk792\!PhD\!Year9Term3\ALI V3\DS-1_Software\Setup_DS1 as an administrator. The correct driver port must first be specified in the .cfg file found in this folder. The driver requires 24V and approximately 3.5 A. Additionally, there is an API guide found in the same folder called CdcCommandSet_102Cust

These two components were returned to Brimrose in early 2018 for some modifications. The details are discussed here: \\utls\users\mnk792\!PhD\!Year9Term3\ALI V3\Data Sheets\AOTF_And_Driver_Modification_201803

OWL 640 Vis-InGaAs Detector

A 640 x 512 pixel InGaAs detector is used in ALI V2. The detector is specially doped to be sensitive from 400 nm – 1700 nm. The documentation for the detector is found here: \\utls\users\mnk792\!PhD\Important Documents\Camera OWL_640_COTS_IM_v1_6_3

Meadowlark Liquid Crystal Polarization Rotator

A twisted neumatic cell polarization rotation unit is used to rotate the polarization state of incoming light into the system. In it’s unpowered state, it causes 90 degrees of rotation. In its powered state, it has no effect on the incoming signal. The documentation is found here: \\utls\users\mnk792\!PhD\Important Documents\Pol Rotator Quality Report

 

Optics Box Enclosure Assembly

A document describing the process of assembling the optics box is found here: \\utls\users\mnk792\!PhD\!Year10Term2\ALI V2\O-Box Assembly

 

Calibration

Calibration files are primarily found here: \\utls\users\mnk792\!PhD\!Year10Term2\ALI V2\BuildAndCalibration

with the Matlab functions found in the “MatlabFiles” folder.