Marian P. Shih

Use of Fourier synthesis holography to image through inhomogeneities

A method for image formation through inhomogeneities is demonstrated. A broad spectral source is decomposed into its Fourier components, and a hologram is recorded at each wavelength through a diffusing medium. When the holograms are synthesized in a computer, a clear image can be formed of the obscured object.

Ultrafast, cross-correlated harmonic imaging through scattering media

A simple upconversion scheme utilizing 40-fs pulses is shown to permit high-contrast imaging of objects obscured by a highly scattering medium when no ballistic component is evident in the scattered light and imaging is performed with any portion of the scattered light pulse. We present a time-gated, inherently low-pass spatially filtered imaging method that minimizes signal-averaging requirements and greatly facilitates imaging under severe scattering (turbid) conditions.

Electronic holographic imaging through living human tissue

Electronic holography and a swept-frequency dye laser are used with the first-arriving-light method to image an absorbing object through the flesh of a human hand. Holography with living human tissue without the use of high-peak-power lasers is made possible by the high sensitivity of the CCD camera as well as its capability for making a large number of holograms in rapid succession, thus enabling the images to be combined to produce a resultant image with an improved signal-to-noise ratio.

Spectral holography for coherence-gated imaging

A spectral-holography application called spectral-decomposition holography forms a recorded image according to optical path length. In this method all wavelength components of a broad-spectrum source simultaneously backlight a nonscattering binary-phase object. A spectral hologram is thus recorded. Subsequent computer processing recovers temporally discriminated images.

Evaluation of holographic methods for imaging through biological tissue

Different holographic methods for imaging through biological tissue are evaluated and compared. The role of the source autocorrelation function is analyzed. A graphical plot for performance evaluation is introduced. Experimental results for the various methods are given, and possibilities for further development are indicated.

Comparison of various holographic techniques for imaging through biological tissue

Five different holographic methods for imaging through biological tissue, as well as other highly scattering media, are described.

Information optics concepts applied to image formation in highly scattering media

We describe a number of methods for imaging into and through highly scattering media, all based in optical imaging processing methods. We describe methods that describe image formation in scattering media in new ways that complement transport theory and other traditional ways.

Challenge of optical imaging through biological tissue

The use of optical radiation for imaging through biological tissue has developed into a major activity. There is now a whole range of methods employed by the many groups attempting to use light to accomplish this formidable objective. We have pursued electronic holography which has some significant advantages but also presents several special challenging problems. We describe various ideas we have developed to overcome them. Finally, we speculate on the ultimate capabilities of these ambitious imaging methods.

Spatial filtering of first-arriving light

The effect of combining low-pass spatial filtering with the first-arriving-light method for imaging through a scattering medium was investigated. The modification is highly effective for media having a significant specular transmission component but is essentially ineffective for media without a specular component.

Coherent optical processing methods for transillumination imaging of biological tissue

We report on a variety of methods for imaging into highly scattering biological tissue, using electronic holography, in combination with a variety of other methods. We present the basic principles of each method and give experimental results. The experiments are carried out with a cooled CCD scientific camera and extensive digital processing.