M. M. Talha

All reflective zoom systems for infrared optics

The results of design effort for infrared zoom systems using all reflective aspheric surfaces are described. Issues such as the paraxial design theory and aberration balancing are discussed in detail. Two all reflective zoom optical systems are disclosed clearly. Both of them are to be used with uncooled infrared detectors. The first design is an unobscured three mirror zoom system without any intermediate image, and the second is a three mirror system with central obscuration which forms an intermediate image. With the design theory further developed, this kind of systems can be designed for cooled infrared detectors, for which cold stop matching is an important issue.

Mathematical and Computer Model for Designing Telescope with Segmented-Mirror

Mathematical and computer modeling of an optical system with a segmented mirror are designed and applied to a telescopic system. The unique feature of this presentation is to establish a center of the segments (sub-aperture arrangement) mathematically that provides six degrees of freedom (i.e. dx, dy, dz, α, β, γ) to each sub-aperture in order to input the mounting errors. To do so, a Visual Basic routine based on CODE Vs COM interface is written that makes it possible to model all types of segmentation modes in a fast and convenient way. Segment results are discussed and the image quality of the design based on these results is evaluated in this paper.

All-reflective optical system design for extreme ultraviolet lithography

All-reflective optical systems, due to their material absorption and low refractive index, are used to create the most suitable devices in extreme ultraviolet lithography (EUVL). In this letter, we present a design for an all-reflective lithographic projection lens. We also discuss its design idea and structural system. After analysis of the four-mirror optical system, the initial structural parameters are determined, the optical system is optimized, and the tolerances of the system are analyzed. We also show the implementation of optimal layout and desired imaging performance.

Design of a compact wide field of view HMD optical system using freeform surfaces

The design of a compact optical system with good image quality for head mounted display (HMD) is particularly demanding since the aberrations, weights, and center of gravity of the display are always critical. One more critical requirement is its wide field of view. We are presenting two designs of an HMD optical system, which have good optical performance while maintaining the compactness. The comparison of their optical performance and other parameters is also presented. Freeform optical surfaces are employed in one of these designs while one aspheric and some spherical surfaces are used in the other design. Freeform surfaces provide more degrees of freedom to design an optical system with less number of elements and hence to reduce the weight of the overall system. Generally, HMD optical systems are tilted and decentered in their nature; it is difficult to get rid of all the aberrations without adding extra optics in such systems. However, freeform optics also provides enough degrees of freedom in this aspect and facilitates the designer to overcome such limitations without additional optics. It is also mentioned that the fabrication technologies of freeform optics are developing now and hence allow the designers to employ such optics elements in their designs. The designing characteristics and results of the two proposed models are also discussed in this paper.

Analysis of stevioside in Stevia rebaudiana

Analysis of stevioside from Stevia rebaudiana was carried out using systematic procedures of various chromatographic techniques including column chromatography yielding the crude stevioside in 12.5%. This procedure was followed by thin layer chromatography and examination of the spots under UV light at 254 and 366 nm, and spraying reagent followed by mixing of fractions on the basis of Rf values. Semi purified fraction obtained from crude stevioside by column chromatography and further evaluation by thin layer chromatography appeared as a mixture showing the presence of four major components (Rf values 0.27, 0.34, 0.42 and 0.60). These finding were similar to reported values for the constituents namely rebaudiosides A, stevioside, rebaudiosides B and steviolbioside, and stevia glycoside reported to occur in Stevia rebaudiana.

Flexure tolerances required to fabricate a freeform HMD optical system

We are presenting the results of a freeform HMD optical system design. The tolerancing analysis is carried out to analyze the optical performance of this system. Results are discussed in detail.

Effect of radius mismatch on performance of segmented telescopic systems

There exist great interests in using segmented mirrors instead of monoliphic primary mirror to build large aperture telescopes. The use of segmented mirrors reduces the difficulties in fabrication, transportation and replication as well as decreases the impact of gravity. In the meanwhile, one of the grand challenges in this approach lies in matching the individual mirrors to yield the form of a continuous surface. The erroneous differences between the global radii of curvature (GROC) of the segmented mirrors have significant influence on image quality. In this paper, we present a model of segmented systems and an analysis technique which reveals the effect of these errors on the image quality. Our analytical results show that the GROC differences have great influence on image quality and the impact remains high despite of using active optics to compensate these errors. The local radii of curvature of individual mirror segment should be used to correct these errors. We propose a new approach to generate compensators that controls the local radius of curvature of each segment efficiently. Finally, through simulation results, we demonstrate that the new compensators can dramatically reduce the effect of radius mismatch.

Comparative analysis of distinct diuretics through urine analysis

Diuretics are used for different diseases and are taken without knowing their adverse/side effects. To create awareness, four popular diuretics, Lasix, Spiromide, Aldactone and Conium were investigated for their effect on body. These were experimented over four volunteers with single and double doses. The urine of these volunteers was collected for analysis of sodium and potassium. The obtained results showed that the effect of medicine remained up to 6 to 12 h. In this duration, the sodium excreted value went up for a certain period and then became almost normal and same was true for potassium. The increase in dosage increased the rate of excretion of the cations and also prolonged the time period of their effects. It is concluded that although Lasix, a potential diuretic but its effects over body were also severe in terms of excretion of ions etc. Similarly, Spiromide was also noted to be a reasonably effective diuretic and its effects are totally different from Lasix in terms of excretion of ions and body weight loss. The other two medicines (Aldactone and Conium) did not show much effect upon excretion etc.