Re: SPPDI® explanatory graphics added


Bruce Griffiths
 

Steve

In principle if there were a switchable beam block in the reference arm then the reference arm and test arm polarisers could be aligned to be orthogonal by:

1) Clock the test arm polariser to block the return test beam

2) Clock the reference arm polariser until a transmission null is achieved

3) Block the return reference beam in the reference arm

4) Clock the source through 90 degrees

5) Clock the test arm polariser until a transmission null is achieved away from the beam blocking segment.

The test and reference arm polarisers are now crossed as required when using an ouput quarter waveplate and a micropolariser array (or clockable linear polariser) in the camera arm.
Fringe contrast can be adjusted by clocking the source.

Alternatively a quarter waveplate in the incident beam could be clocked to rotate the plane of polarisation of the return beam. 

Bruce

On 13/07/2022 04:13 The Light Whisperer® <info@...> wrote:


Bruce,

An additional purpose of the polarization cleaner used on earlier models of the SPPDI® was to enable adjustment of the optical power emitted from the SPPDI. This was accomplished by simply rotating the diode laser until the power transmitted through the polarization cleaner fell below the Class 1 limit. However, this concern turned out to be unfounded, due to the fact that the laser power emitted into an f/8 beam by the cheap diode lasers which we use is already very low, and is further reduced by the NPBS cube that the beam passes through before leaving the SPPDI enclosure.

Steve

------ Original Message ------
From "The Light Whisperer®" <info@...>
Date 7/12/2022 8:18:41 AM
Subject Re: [Interferometry] SPPDI® explanatory graphics added

Bruce,

The polarization cleaner that was originally used in the earlier models of the SPPDI® is no longer used. The degree of polarization present in low-cost diode lasers was found to be sufficient to eliminate the need for the polarization cleaner that was previously bonded to the face of the NPBS cube adjacent to the diode laser.

Steve

------ Original Message ------
From "Bruce Griffiths" <bruce.griffiths@...>
Date 7/11/2022 11:46:18 PM
Subject Re: [Interferometry] SPPDI® explanatory graphics added

Steve

The pictorial representation of the SPPDI doesn't show the polarisation cleaner mentioned in the manual.
Is the polarisation cleaner no longer used? 

Bruce
On 23/06/2022 03:35 The Light Whisperer® <info@...> wrote:


I appreciate the patience of Dale Eason in allowing me the occasional use of this Bath interferometer related forum to post an occasional reference to my SPPDI® product. For those who may be interested, a pictorial description of the SPPDI® has been added to the introductory section of the kerryos.com website. See https://kerryos.com/introduction/.

Thanks,
Steve W.





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