28 October 2004
The technique of simultaneous spectral differential imaging (SSDI) is used to image directly brown dwarfs and exoplanets around nearby stars. An analytical PSF model is first presented with numerical simulations to estimate the PSF noise attenuation performance. A three-wavelength infrared camera (TRIDENT) implementing the SSDI technique is then described. Results from a survey of 35 nearby stars carried out with TRIDENT at the Canada-France-Hawaii telescope are presented. Performance estimates show that a companion 9.5 magnitudes fainter than a star is detectable (6 sigma) at 0.5" separation. An analysis of the observations suggests that non-common path aberrations between TRIDENT optical channels are the limiting factor preventing further PSF noise attenuation. A new camera concept using a multi-wavelength detector featuring a microlens array combined with micro-filters is presented to overcome the non-common path aberration problem. Another imaging technique, differential angular imaging, is also discussed to obtain a reference PSF in each optical channel while observing a target. Finally, the accuracy of FFT-based image shifting, scaling and rotating algorithms is studied to show that a companion 10^9 times fainter than a star can theoretically be detected by those algorithms.