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TIMMI2 diffraction-limited mid-infrared images of a multipolarproto-planetary nebula IRAS 16594-4656 and a young [WC] elliptical planetarynebula IRAS 07027-7934 are presented. Their dust shells are for the first timeresolved (only marginally in the case of IRAS 07027-7934) by applying theLucy-Richardson deconvolution algorithm to the data, taken under exceptionallygood seeing conditions (<0.5"). IRAS 16594-4656 exhibits a two-peakedmorphology at 8.6, 11.5 and 11.7 microns which is mainly attributed to emissionfrom PAHs. Our observations suggest that the central star is surrounded by atoroidal structure observed edge-on with a radius of 0.4" (~640 AU at anassumed distance of 1.6 kpc) with its polar axis at P.A.~80 degrees, coincidentwith the orientation defined by only one of the bipolar outflows identified inthe HST optical images. We suggest that the material expelled from the centralsource is currently being collimated in this direction and that the multipleoutflow formation has not been coeval. IRAS 07027-7934 shows a bright,marginally extended emission (FWHM=0.3") in the mid-infrared with a slightlyelongated shape along the N-S direction, consistent with the morphologydetected by HST in the near-infrared. The mid-infrared emission is interpretedas the result of the combined contribution of small, highly ionized PAHs andrelatively hot dust continuum. We propose that IRAS 07027-7934 may haverecently experienced a thermal pulse (likely at the end of the AGB) which hasproduced a radical change in the chemistry of its central star.Comment: 35 pages, 8 figures (figures 1, 2, 4 and 6 are in low resolution)  accepted for publication in Ap

Revealing the Mid‐Infrared Emission Structure of IRAS 16594−4656 and IRAS 07027−7934