Digital Holographic Microscope

Single Shot Full Resolution Digital Holographic Microscope (DHM) instrument

Most microscopes used in current Bio-medical laboratories require staining/labelling of cells thus potentially damaging them. When light waves interact with transparent label-free cells they are not absorbed but do get a “phase” imprint. The phase of light waves cannot be measured directly but can be recovered using the principle of interference. Our research work at IIT Delhi on interferometric phase imaging led to a novel methodology that can break the traditional limits on single shot resolution and noise performance of interferometric phase measurement. Apart from several high quality publications on this topic IIT Delhi currently holds a granted US patent on this idea. In collaboration with Holmarc Opto-Mechatronics Pvt. Ltd., we have now taken our basic science work to a DHM device (see photo) which is now installed in IIT Delhi’s Central Research Facility for generic use by all interested researchers. This system can image transparent label-free cells with full diffraction-limited lateral resolution (~0.5 um) and simultaneously provides depth profiling accuracy down to less than 50 nm. Our novel approach to single-shot phase imaging has bypassed several hardware components required in prior-art phase shifting DHM configurations thus reducing the system cost without adversely affecting the quantitative phase imaging performance. In a collaboration with AIIMS we have already shown the value of this technology in classifying cervical cells for cancer stage detection. The product can find important new applications in basic Bio-science research and diagnostics and we are open to new inter-disciplinary collaborations on the use of this technology.

Contact: Prof. Kedar Khare.

    Selected publications/patents:

  1. K. Khare, Samsheerali P. T., Joby Joseph, “Single shot high resolution digital holography”, Optics Express 21, 2581-2591 (2013).

  2. M. Singh, K. Khare, A. K. Jha, S. Prabhakar, R. P. Singh, “Accurate multipixel phase measurement with classical light interferometry”, Physical Review A 91, 021802(R) (2015).

  3. K. Khare, J. Joseph, Samsheerali PT, “Image recovery from single shot digital hologram”, US9135682B2 (2015) [Granted to IIT Delhi].

  4. N. Pandey, A. Ghosh and K. Khare, “Two dimensional phase unwrapping using the transport of intensity equation”, Applied Optics 55, 2418-2425 (2016).

  5. M. Singh and K. Khare, "Accurate efficient carrier estimation for single-shot digital holographic imaging," Optics Letters 41, 4871-4874 (2016).

  6. J. Mangal, R. Monga, S. R. Mathur, A. K. Dinda, J. Joseph, S. Ahlawat and K. Khare, “Unsupervised organization of cervical cells using brightfield and single-shot digital holographic microscopy”, Journal of Biophotonics 12, e201800409 (2019).

  7. R. Malik, P. Sharma, S. Poulose, S. Ahlawat, K. Khare, “A practical criterion for focusing of unstained cell samples using a digital holographic microscope”, Journal of Microscopy 279, 114-122 (2020).