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Combined optical and acoustical method for determination of thickness and porosity of transparent organic layers below the ultra-thin film limit Rev. Sci. Instrum. 82, 103111 (2011) Spatial anisotropy of the acousto-optical efficiency in lithium niobate crystals J. Appl. Phys. 108, 103118 (2010) Observation of the forbidden doublet optical phonon in Raman spectra of strained Si for stress analysis Appl. Phys. Lett. 97, 041915 (2010) High-resolution laser lithography system based on two-dimensional acousto-optic deflection Rev. Sci. Instrum. 80, 085105 (2009) Additional information on J. Appl. Phys.When chopped light impinges on a solid in an enclosed cell, an acoustic signal is produced within the cell. This effect is the basis of a new spectroscopic technique for the study of solid and semisolid matter. A quantitative derivation is presented for the acoustic signal in a photoacoustic cell in terms of the optical. thermal, and geometric parameters of the system. The theory predicts the dependence of the signal on the absorption coefficient of the solid, thereby giving a theoretical foundation for the technique of photoacoustic spectroscopy. In particular, the theory accounts for the experimental observation that with this technique optical absorption spectra can be obtained for materials that are optically opaque.

This paper proposes a new bit allocation algorithm, capable of efficiently allocating a given quota of hits to an arbitrary set of different quantizers. This algorithm is useful in any coding scheme which employs hit allocation or, more generally, codebook allocation. It produces an optimal or very nearly optimal allocation, while allowing the set of admissible hit allocation values to be constrained to nonnegative integers. It is particularly useful in cases where the quantizer performance versus rate is irregular and changing in time, a situation that cannot be handled by conventional allocation algorithms.

Asymptotically Optimal Block Quantization ALLEN GERSHO, SENIOR MEMBER. IEEE Abmwet-In 19U3 W. R. Bennett used a compandiug model for uommiform quantlzation and proposed the formula for the mean-square quantizing error where N is the. number of level&p(x) is the probability density of the input, and E'(x) is the slope of the compressor curve. The formula, an approximation based on the assumption that the number of levels is large and overI& distortion is negligible, is a useful tool for analytical studies of quantfzation. This paper gives a bedstlc argument generallhg Bemett's formula to block quantization wbere a vector of random variables is quantized. The approach is again based on the. asymptotic situation where N, tke number of quantized output vectors, is very large. Using the resulting heuristic formula, an optimhtlon is performed leading to an expression for the minimum quantizing noise attainable for any block quantizer of a given block size k. The results are consistent with Zador's results and speciaiize to known results for tke one-and two-dimensional casea and for the case of White. block length (k+m). The same heuristic approach also gives an alternate derivation of a bound of Elias for multidimensional quantization. Our approach leads to a rigorous metkod for obtaining upper bounds on the minimum distortion for block quantizers. In particular, for k = 3 we give a tigkt upper bound that may in fact be exact. 'Ihe idea of representing a block quantizer by a block "compressor" mapping followed with an optimal quantizer for uniformly distributed random vectors is also explored. It is not always possible to represent an optimal quautizer with tbis block companding model.

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