In a message dated 2008/02/26, PETERS_RD@.......... writes:

> With the attention so frequently given to optical-type detectors, I am 
> surprised that nobody has yet mentioned what I believe to be the most clever 
> invention of them all. The great R. V. Jones, who is best known and quoted in 
> seismology for his work with capacitive sensors, while at Aberdeen invented a 
> modified optical lever that uses Ronchi rulings.  Ronchi is in this modern era 
> largely unknown, but his contributions in the field of figure-testing of 
> optical components was of truly great significance.  Those who want to study 
> Jones' system can download the following paper: 
> http://iopscience.iop.org/0950-7671/38/2/301/pdf

Hi Randall,

       Ronchi gratings have certainly been mentioned in past psn Emails. 
There are ate least two problems with this approach. Firstly it requires the 
production of fairly expensive gratings. Secondly the line intensities are likely 
to be very low. 

       I believe that Zumberge was using this type of sensor. 
http://gravity.ucsd.edu/research/SIFO/

       Since you can get resolutions of less than 10 nano metres with a 
couple of 7 sq mm Si photocells and a small filament bulb. what advantage do you 
see in using optical fringe signals? 

       Have you any suggestions for reducing the $30 cost for just 9 pages of 
a 1961 article?

       Regards,

       Chris Chapman         
In a me=
ssage dated 2008/02/26, PETERS_RD@.......... writes:



With the attention so frequentl=
y given to optical-type detectors, I am surprised that nobody has yet mentio=
ned what I believe to be the most clever invention of them all. The great R.=
 V. Jones, who is best known and quoted in seismology for his work with capa=
citive sensors, while at Aberdeen invented a modified optical lever that use=
s Ronchi rulings.  Ronchi is in this modern era largely unknown, but hi=
s contributions in the field of figure-testing of optical components was of=20=
truly great significance.  Those who want to study Jones' system can do=
wnload the following paper: http://iopscience.iop.org/0950-7671/38/2/301/pdf=




Hi Randall,



       Ronchi gratings have certainly been men=
tioned in past psn Emails. There are ate least two problems with this approa=
ch. Firstly it requires the production of fairly expensive gratings. Secondl=
y the line intensities are likely to be very low. 



       I believe that Zumberge was using this=20=
type of sensor. http://gravity.ucsd.edu/research/SIFO/



       Since you can get resolutions of less t=
han 10 nano metres with a couple of 7 sq mm Si photocells and a small filame=
nt bulb. what advantage do you see in using optical fringe signals? 



       Have you any suggestions for reducing t=
he $30 cost for just 9 pages of a 1961 article?



       Regards,



       Chris Chapman    &n=
bsp;