We start with only the finest quality!  Fine or precision annealed low

 

expansion borosilicate glass substrate, Schott Supremax 33,

 

unless otherwise noted. Each substrate is tested under polarized

light for internal strain and striae. No work will commence on any

substrate unless it passes this test, including optics sent to us for

 

re-figuring.  All of our substrates are free of any edge chips.



After diamond generation, fine grinding, polishing, and figuring, each

 

optic receives several hours of testing in our atmospherically


controlled shop. We use not one, but several precise optical tests.

 

The results from each test are cross-checked against each other in

 

order to provide an accurate qualitative and quantitative assessment

 

of the optical quality.

 

 

Our testing methods include.
 



*Foucault-Null Test: Used to obtain a reading of the overall

correction and to inspect the optical surface for smoothness. The

 

overall correction reading provided by this test is verified against

 

results obtained from Interferometry. In most cases we use a double-

 

pass null test.

 


*Figure of Revolution Test: Used for detecting stress induced flexure

errors and astigmatism. The primary mirrors manufactured at

Ostahowski Optics, Inc. are tested in the horizontal optical axis using

 

an optical mounting sling. The most common and severe stress

 

flexure aberrations are astigmatism and trefoil. Each optic receives

 

extensive testing to determine if the optical surface is exhibiting

 

stress flexure or true astigmatism. The astigmatic error that is not

 

induced by mounting stress is always removed during optical

 

figuring. Every primary must pass this surface of revolution test.

 

*Interferometric Testing: Interferometric testing is the standard that

aerospace industry, professional optical labs, government labs, and

 

well informed consumers, use for a quantitative assessment of the

 

optical wave front quality. Interferometry is a time consuming and

 

expensive process requiring a high degree of technical expertise. It

 

produces accurate test results enabling us to consistently produce

 

outstanding mirrors. This is the final test that all Ostahowski Optics,

 

Inc.. mirrors undergo and must pass.

 

 

We employ several different types of interferometers, each

 

has a specific use depending upon the optic, or system. During

 

interferometric testing the shape of an optic's wave front is

determined by superimposing its wave front over a reference wave

front that is certified to be highly accurate. Constructive and

destructive interference created between the superimposed wave

fronts generate the interference fringes. A CCD camera is then used

 

to capture an image of the interference fringes and send it to a

 

computer. Interferometric fringe analysis software is then used to

 

analyze the data points along the fringes and accurately determine

 

the deviation between the two wave fronts. Interferogram averaging

 

minimizes the effects of any air currents that may be in the light

 

path during testing providing accurate information about the true

wave front quality. The fringe analysis software then generates us a

 

detailed report. Mirrors certified by zonal Foucault test rarely attain

 

the same quality of results when tested by an interferometer and

almost always overstate the quality of the mirror being tested.


 

Test Data Provided

Ostahowski Optics, Inc. test data reports contain the following

information:

                        Interferogram


                        Strehl Ratio (primary optics and optical systems)

                        RMS Wave front Error

                        Peak to Valley Wave front Error

                        Wave front Map

The Process

Bad Anneal

Good Anneal

Generation

Fine grind inspection

Polishing

After polish Inspection

Surface of revolution

Interferogram

Hartmann Screen

Phase map