SUMMARY OF THE DOCTORAL THESIS ON
Contributions to the amelioration of the optical systems quality through the improvement of the manufacturing technologies
The thesis belongs to the wider area of optical systems quality amelioration and is placed at the crossroad of the synthesis and
analysis measures.
The necessity to improve the quality of optical devices including optical components produced through classical technology
methods has determined some specialised companies to explore and develop new manufacturing technologies for acquiring
aspherical optical components based on quality and high efficiency. By combining spherical and aspherical components and using
new optical calculation theories and special software for the optical evaluation of the device the aberrations introduced by the
optical sphere can be examined successfully, thus leading to the achievement of devices including a lower number of lens and to
major advantages, such as: the decrease of the size and mass of the optical device, the increase of the eyeshot, image quality and
reliability, etc. To correct the aberrations introduced by the spherical optics, the classic theory uses other lens, also spherical,
complementary, introducing positive and negative aberrations and determine the decrease of the subassembly aberrations.
The optical surfaces, especially the complex profile ones, can not be achieved satisfactory and cost efficiently through the classic
grinding and polishing. The real advantages of the optical aspheric components stimulated the manufacturers to develop specific,
efficient and reproducible technologies, for the generation and finishing of the aspherical surfaces in accordance with the desired
quality parameters. The technological methods used are hybrids of the classic manufacturing methods (the mechanical generation
and the medium and fine grinding as well as the polishing of the component on classical polishing devices for spherical surfaces)
or mostly unconventional technologies, created initially for other technological domains (plastics injection, heat compressing of
glass parisons, metal borizing, thin layers vacuum coating).
The difficulties in using non conventional technologies were mainly due to the essential differences in the optical glass
manufacturing technologies and the metal or plastics manufacturing ones (for some kinds of mirrors) and especially due to the
differences in terms and technological concepts used in each of these fields.
The present evolution of the optical systems reflects a prominent preference for compactness and miniaturization, associated with
an increase of the optical systems accuracy, as a result of the replacement of the image analyser - the human eye- with its limits,
by an electronic control system.
Within this context it became necessary to develop optical components which, due to their structure, size and optical
performance, should comply with these requirements. Besides the classic optical components, spherical lens and prisms, there are
used special optical components, such as aspherical lens and mirrors, cylindrical lens, Fresnel lens, Hopkins lens, GRIN lens with
a variable refraction index.
The important optical devices manufacturers have achieved advanced optical systems including one or more aspherical lens
which improve the system performance. Some of the applications using such optical components are: miniature aspherical lens
used for laser diodes, lens for video cameras, lens for thermal chambers, projection lens, focus lens, etc.
The thesis shows the influence of the execution and assemblage errors on the quality of the images provided by optical and
optoelectronic systems. The assessment of the quality of the images developed by optical systems is achieved depending on the
effects of the reduced aberrations which are treated diffractionary and on the effects of the big aberrations, treated geometrically.
The use of well-defined polynomials to build up the analytical expression of the aberration based on the discrete values
determined through the rays plotting is more accurate.
The modelling and simulation of the influence of the execution and assemblage errors on the quality of a complex optical system
image were achieved by means of a specialised software application and the conclusions expressed the necessity to achieve the
study by use of simulation for each projected optical system, which is the sole way to establish rationally the permissible
deviation for each dioptre. At the same time, there are described some conventional and non-conventional manufacturing
technologies for the lens which are included in the optical systems structure
The multiple advantages of using aspherical lens determined the constant development of the manufacturing technologies fore
these types of lens.
Presently, the aspherical lens surface is achieved by chipping and the profile is generated by a larger contact, mainly punctiform,
between the device and the processed surface - this process is similar to borizing. The accuracy of the generated surface depends
mainly on environmental conditions, accuracy of the machine tool, depreciation of the chipping machine and on the existing
vibrations.
The thesis have also emphasises the main technological contributions meant to improve the quality of the images provided by
optical and optoelectronic systems.
The replacement of the classic receiver - the human eye - with electronic systems analysing the images obtained by means of an
optical device, as well as the use of UV wavelengths requires optical components of higher accuracy. These aspects determined
the development of technologies allowing the acquiring of surfaces with errors of shape/minimum roughness without defects of
the surface or under layer, which are necessary especially for special applications in fields like power lasers, photolithography at
low wavelengths, optical micro and nanostructure components.
The approached topic may be considered as an in depth study within a less common field at national level, but used practically
both in the military and in the civil field, and it is far from being exhausted; its existing applications could be improved in view
of creating new optical and optoelectronic systems necessary for the acquiring of qualitative images.