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Interferometer "OPTOTL-ICO - 60"
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At the beginning - several words about the history of our development. The need for the device to check optical surface accuracy, especially spherical one, arose at our own production that is specialized in manufacturing of high-precise optical components. However, the resources of our small company did not allow us to purchase expensive certifying measuring equipment. Thus, we made the decision to work up and produce the device ourselves, since we already had the necessary experience in this engineering field.
Gradually we formed the the conception as follows. We will not compete with serious devices of the companies like ZYGO, Optotech, etc., who state the accuracy lambda/100 and higher. The accuracy of our device is much lower - lambda/10. But our goal also differs - we need a workshop device that is placed near manufacturing machines and that opticians will work with themselves.
The spherical surface interferometer is applied for technological test of the accuracy of polished optical plane and spherical surfaces straightly at the working place next to the working machines at optical production.
The surface analysis interferometer is worked up on the basis of well-known Fiseau-scheme, but some new assemblies are developed and used in it's design; the corresponding applications for inventions are submitted.
In OPTOTL-ICO-60 the software FastInterf is used (the detailed description is attached) and it is modernized to simplify the work of unqualified users. |
The main distinguishing features of the device OPTOTL-ICO -60 are as follows:
- small size in order to locate the device practically at any place of optical department;
- simplicity of operating with the device, which allow to quickly teach any optician to work with it;
- quickness of adjustment - optician is diverted for surface measurements for a short time, which is due to the big field of vision of adjusting channel and to the presence of additional adjusting channel monitor;
- module principle of construction, which permits to easily modernize the devise and use the same construction parts at different working places within the same optical department, avoiding the expenses for purchasing of additional equipment.
The whole device consists of:
- the main optical-mechanical block
- two minimonitors for adjusting and visualization of interference picture
- standard settings kit
- computer with software
Characteristics of the device
The main block:
- Collimator aperture, mm ................................................................................60
- Sizes of the main block (without lighter), mm
- Diameter ...................................................120
- Length..........................................................450
- Light source ...............................................HeNe laser
- Multiplicity of the image scale change (Zoome) - 3X
- Manual focusing in wide limits to exclude the affect of diffraction
- Vertical arrangement "standard surface above - components below" - it is suitable to testing a block of parts
- Tilting vertical post for testing of edge areas of steep surfaces and components located at the edges
- The possibility of measuring of passing through wavefront (at the presence of additional standard)
Monitors:
- Separate monitor of adjusting channel
- Monitor for visualization of interference picture
- Note: the presence of two located nearby monitors considerably simplifies the adjusting procedure.
Kit of standards:
- The number of settings in a standard set, pcs .........................16
- Certified accuracy of a standard surface, lambda ...................0.1
- The limits of settings' aperture measurements F# .......1:0.8 - +/-1:15
- The limits of radiuses of tested surfaces at the condition of full settings set, mm ..............1000CC -900CX
- The possibility of producing the special settings to enlarge the range of measured radiuses
Software:
- Calculation of all standard parameters which define the accuracy of optical surface:
- spread of errors (P-V);
- root-mean-square (RMS)
- defocussing (poer)
- Aberration subtraction including the 3rd order, and also Cernike polinomial calculation;
- The result can be presented in various forms, in the form od 3D surface topography too;
- Presentation of generated interference picture - for visual estimation of calculation correctness.
Our experience shows that one device is not enough even at small department with less than 15 opticians who polish various precise optical components - opticians periodically form a line to interferometer. In ideal situation each optician should have his own device and this caused the second part of the name ICO (Interferometer Comes to Optician), or in Russian version ИКО (Интерферометр Каждому Оптику).
At the beginning, however, it is possible to manage with three devices. And it is not necessary to purchase immediately three complete sets - it is quite enough to establish:
- three main blocks
- one computer with the software
- one kit of settings
Of course, several users can not work with one software at the same time. But this will not slow down the work, because the adjusting, which takes the most time, is accomplished at the main blocks that are equipped with their own monitors to fix and watch interference pictures.
With the set of cables, that are available, it is possible to make all the necessary connections
between remote (up to 5-6 meters) devices.
In conclusion we emphasize that our device is the mean of technological, not attestation, test. Thus, strict metrological certification was not developed. However, each standard setting was certified by ZYGO interferometer at special measuring laboratory.
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