On 31st October 2015, SEMICAPS Corporation filed an IPR with the USPTO to re-examine the validity of US Patent 7733100. This is the frequency mapping patent claiming a method used in semiconductor analysis employing laser probing techniques.

The main reasons cited in this action are prior art and obviousness. Among many publications on early laser-based spatial mapping techniques cited in the IPR are: US Patent 5260648 by Brust, technical papers G. David, et al. (Analysis of microwave propagation effects using two- dimensional electrooptic field mapping techniques, Optical and Quantum Electronics, vol. 28, 1996, pp. 919-932), and D. Jager, et al (Fundamentals of Optical Beam Testing, Microelectronic Engineering, Vol. 24, (1994), pp. 327-339).

Also included in the IPR is a detailed expert analysis of the patent written by Harley Heinrich, PhD. Dr. Heinrich is widely considered to be the “father” of laser probing techniques used to recover various types of signals through the backside of ICs.
https://ptabtrials.uspto.gov/prweb/PRServlet and search for IPR2016-00120.