Autofocus in infrared microscopy

Autofocus (AF) is a widely investigated subject in the fields of natural scene images, industrial assembly and biologic microscopy. This paper proposes a new effective AF method for infrared (IR) microscopy in the context of the Integrated Circuit industry (IC). The proposed method operates in the wavelet domain using a custom orthogonal wavelet for the 2D Discrete Wavelet Transform (DWT). The quality criterion of our AF algorithm relies on the standard deviance of the DWT coefficients, computed per subband and per level. Tested on several optical magnifying lenses, our method is robust time-efficient, and usable on-the-fly in the IC location system.