Amitabha Basuray

Arithmetic operations in optical computations using a modified trinary number system

A modified trinary number (MTN) system is proposed in which any binary number can be expressed with the help of trinary digits (1, 0, 1 ). Arithmetic operations can be performed in parallel without the need for carry and borrow steps when binary digits are converted to the MTN system. An optical implementation of the proposed scheme that uses spatial light modulators and color-coded light signals is described.

Carry-less arithmetic operation of decimal numbers by signed digit substitution and its optical implementation

Abstract A new system of representing decimal numbers has been attempted where modified signed digit substitution rules are used to achieve arithmetic operations without carry/borrow and in parallel. Optical implementation of the suggested method is proposed.

New technique of arithmetic operation using the positional residue system

A simplified arithmetic digitwise positional operation is proposed that uses only moduli 2 and 5 of the residue number system.

A real-time optical parallel processor for binary addition with a carry

Abstract A bichannel optical shadow casting (OSC) technique has been proposed for logic operation and addition of multi-bit binary numbers. In case of addition the “carry” is accomodated by spatial placement of channels. Optoelectronic half and full adders, using spatial light modulators (SLM), optical to electrical converters, beam splitters and mirrors, form additional building blocks in the proposed processor, where operations are performed in parallel. Limitations are discussed.

Coherent moire technique for obtaining slope and curvature of stress patterns

A method for studying the stress-induced birefringence over the area of a sample by simultaneous application of shearing interferometry and moire techniques is dealt with. This is a method by which one can have the fringe pattern for the first and second derivative of the birefringence distribution in the form of the slope and curvature of the test wavefront. There is, however, a method of obtaining the second derivative fringe system by using a four-exposure holographic technique in which the pattern is generated by shearing of two holograms of deformed surface. This is related to stress distribution in the structure under test. In the presented method, on the other hand, the test wavefront carries the information of stress distribution in terms of birefringence. The suggested experimental setup can provide the slope and curvature of the test wavefront in a single exposure.

Measurement of gradient refractive index profile using a birefringent lens

The shape, depth, and maximum change in refractive index profile are of the most important parameters to be controlled when de- veloping gradient refractive index (GRIN) lens blanks. Generally refrac- tive index profiles are measured by standard interferometers such as Mach-Zhender, Twyman, and Shearing interferometers. These methods generate a large amount of data and need rigorous computation. A new kind of deflectometery is reported that can measure a GRIN profile using the interference pattern generated by a birefringent lens. Results based on this method are presented for radial GRIN glasses developed by Ag 1 -Na 1 and Na 1 -Li 1 ion exchange in alkali aluminosilicate glasses.

Birefringence measurement using a confocal setup with a pair of birefringent lenses

A confocal microscopic setup with a pair of birefringent lenses having their crystal axes crossed is used to measure birefringence of thin samples. The method can be used to measure phase down to the order of /10. The fast and slow axes of the object also can be identified. The principle of the method along with the experimental setup is described. Some first-order experimental results are also presented.

Measurement of refractive index profile of GRIN glasses

A method for measurement of refractive index profile of a GRIN system is developed based on a longitudinal interferometer using a birefringent lens. The fringe pattern so generated is made to traverse through the sample under test. The modification of the fringes gives a measure of the refractive index profile. The fringe patterns both in presence and absence of the test samples are grabbed by a CCD camera and further processed by a computer. The basic software required for the same is being developed. Some experimental results are presented.

Application of a birefringent lens in photoelastic studies using a coherent moiré technique

Abstract In photoelastic investigations, one uses the property of stress induced birefringence for stress analysis. Normal polariscopes are used for such studies. However, the accuracy of the methods is low. For better accuracy, interferometric and holographic methods are generally used. Holography, along with a shearing technique, is also used to obtain partial derivatives of displacement with respect to spatial co-ordinates. In these methods, the resultant fringe pattern is obtained from the mutually shifted holograms and the generation of such patterns requires four exposures altogether. The present paper represents a method based on a coherent moire technique for studying the first derivative of a stress pattern using birefringence properties. The analysis seems to be very similar to holographic techniques as both produce second order fringes. The advantage of this method is that it requires only one exposure. The basic principle as well as some experimental results are presented.

Binary to modified trinary number system conversion and vice-versa for optical super computing

With the demand of the super fast processing and handling of huge volume of data the scientific workers in the field of computer and optics felt the importance of optical computation with multivalued logic. One of the most important number system suitable for optical computation with multivalued logic is the modified trinary number (MTN) system because of its carry and borrow-free operations. At this juncture to avail the advantages of both the Binary and MTN system the conversion from one system to another is most important. In this paper we have communicated the conversion from Binary to MTN and vice-versa including the mixed MTN with details of optoelectronic circuit implementation.