Two-dimensional lock-in amplifier systems for microscopic imaging

We have previously developed two-dimensional lock-in amplifier systems that can detect very small changes in the light intensity distributions of images. In general, optical microscope systems have poor resolution in the depth direction rather than in the focal plane, and thus it is important to improve the depth resolution to achieve three-dimensional imaging with high-resolution. In this paper, we present a new technique to improve the depth resolution by implementing lock-in amplifier technology. In this technique, a lock-in amplifier system is used to obtain derivatives of the image intensity in the depth direction by using these derivatives, the depth resolution can be improved by a factor of 3.5. We believe that the systems should be applicable in the two-dimensional measurement of optical information