Ivan D. Nikolov

Optical plastic refractive measurements in the visible and the near-infrared regions

Some new refractometric results are obtained in the visible and the near-infrared spectral regions. The main optical plastics are analyzed: poly(methyl methacrylate), polystyrene, polycarbonate, and styrene acrylonitrile. New materials, such as methyl methacrylate styrene copolmer, CTE-Richardson, Zeonex, Optorez, and Bayer are examined. The refractive indices are measured for wavelengths from 435.8 to 1052 nm with a new device. Abbe constants and dispersion coefficients are calculated. The measured and computed data is intended for designers and technologists.

Measuring the refractometric characteristics of optical plastics

Ten types of American, Japanese, and German optical plastic (OP) materials are examined. The principal OPs are analysed: polymethyl methacrylate, polystyrene, polycarbonate, and styrene acrylonitrile. Refractive indices are measured and calculated for the principal and some new applicable OPs, namely NAS-21 Novacor, CTE-Richardson, Zeonex E48R, Optorez 1330 and Bayer for wavelengths from 435.8 to 1052 nm. A theoretical examination was made for computer modelling of OPs indices using Cauchys dispersion formula. The dispersion coefficients and Abbe constants are calculated. The OPs indices computed for numerous laser wavelengths 442–1060 nm are presented. A more effective device and technology for the measurement of refractive index of OPs is realized with an accuracy of ±0.001.

Temperature dependence of refractive characteristics of optical plastics

In this study we investigate the variation of refractive characteristics of optical plastics with temperature in the range of 10 to 50 oC. We have measured the indices of several optical polymers as Optorez 1330, Zeonex E48R, Polymethyl methacrylate, S-low styrene and Bayer by means of the deviation angle method. The obtained refractive index data is presented at five standard spectral lines in the visible region. A decrease of refractive index values with increasing temperature is observed. Dependence on measuring wavelength is also noticed. We have calculated the temperature coefficients of refractive indices of the studied optical plastics. Charts of refractive index of some of the materials versus temperature are presented. Temperature dependence of dispersion curves based on Cauchy-Schotts approximation and Abbe numbers is also considered.

Laser measurements of optical plastics

A He-Ne laser device has been used for refractometric measuring of a number of optical plastic (OP) specimens. We applied an ellipsometric laser system for the index of refraction initial determination. A table of the experimentally obtained refractive indices of various types of the principal and some new developmental OPs at the laser wavelength λ=632.8 nm is illustrated. The dispersion coefficients of ten American, Japanese and German OP samples were computed using a modified Cauchys dispersive equation. A table of OPs refractive indices calculated at twenty laser wavelengths in the spectral area from 405 nm (GaN LD) to 1064 nm (YAG devices) is presented.

Optical properties of thin polymer films

In this report three types of optical polymer thin films deposited on glass substrates are investigated. Transmission spectra of the polymer samples are obtained in the range from 400 nm to 1500 nm. A laser microrefractometer has been used to measure the refractive indices of the examined materials at 406, 656, 910 and 1320 nm. Dispersion properties of the polymer films are analyzed on the base of the Cauchy-Schotts and Sellmeier`s approximations. Dispersion coefficients are calculated and dispersion charts in the visible and near infrared spectral regions are presented and compared. Abbe numbers of mean and partial dispersion of the polymer films are obtained. Calculation of refractive indices at many laser emission wavelengths in the considered spectral range is accomplished.

Investigation of optical properties of thin polymer films

Several types of optical polymer materials produced by Eastman Chemical Company were studied. Thin films deposited on glass substrates from solutions were prepared and studied to reveal their refractometric, dispersive and transmission properties in the visible and infrared spectral regions. The refractive indices were measured by means of two modifications of a laser microrefractometer.

Optical properties of plastic materials for medical vision applications

Several types of optical polymer materials suitable for ophthalmic or medical vision applications have been studied. We have measured refractive indices of studied plastics at various wavelengths in the visible and near-infrared spectral regions. Important optical characteristics as Abbe numbers, dispersion coefficients and curves, principal and relative partial dispersion have been evaluated. Calculated refractometric data at many laser emission wavelengths used for medical surgery, therapy and diagnostics is included. As an example of a medical vision application of plastics, optical design of a micro-triplet for use in disposable endoscopes is presented.

Three-wavelength laser microrefractometer

A three-wavelength laser microrefractometer has been assembled and standard liquids have been used for calibration of the experimental set-up. Refractive indices of polymer solutions of Polycarbonate, Polyarylate, Polyester, Nylon, Copolyester A and Copolyesters B are measured. Experimental results of the examined samples are obtained at laser wavelengths of 532 nm, 632.8 nm and 790 nm. A standard uncertainty of ± 2×10-4 has been achieved applying gomiometric table with 1-arcmin resolution. Specific refraction of the investigated polymer materials and their solutions are determined. The dispersion coefficients of Sellmeiers and Cauchys equation are calculated and comparative dispersion curves are illustrated.

All-plastic optical design for NIR region

A number of optical plastic materials are examined. The indices of refraction are measured in the visible and near- IR spectral regions from 435.8 nm to 1052 nm. Some obtained data and Abbe constants are presented. The glass libraries of the optical design software packages are updated. The spherochromatic aberration balancing is analyzed during the all-plastic doublet and triplet synthesis for a working wavelengths interval from 600 nm to 900 nm. Two achromatic triplets are designed intended for NIR region. Three all- plastic 3X magnifiers are developed for NV goggles. The optical configurations are given. The aberration corrections are evaluated. The obtained optical performance is illustrated. Some conclusions for the trends in all-plastic optical design are drawn.

Hybrid plastic-glass optical systems

The principal optical plastics are polymethyl-metacrilate (PMMA), polystyrene (PS), polycarbonate (PC), and methylmetacrylate styrene copolymer (NAS). The optical properties of plastics are rather good for different designing configurations. Optical system design using plastic materials is a design target close to that of glass lenses [1]. Using PMMA and PS or PC one can synthesized doublet objective built by separated positive and negative elements. The Gaussian form of the achromat may consist of two uncemented lenses. The achromatic magnifiers and eyepieces for goggles permit a nonanastigmatic and orthoscopic field of view. Some aspheric surfaces can be applied to reduce the systems residual aberrations. The most important spectral regions of the plastic optical systems are VIS and NIR areas at wavelength about 700 nm. Using some new optical materials one can improve the aberration correction [2]. We may elevate the aperture ratio up to F/2 with a better optical performance adding a third element to the achromatized doublet.