Red blood cells microrheologic and size distribution parameters in vascular diseases: evaluation by laser techniques

We present a partial aperture imaging method based on the recently developed incoherent imaging process termed interferenceless coded aperture correlation holography. The observed 3D scene is captured by a single camera shot and reconstructed by a non-linear technique. Summary Interferenceless coded aperture correlation holography (I-COACH) is a motionless, non-scanning, incoherent 3D imaging technique [1]. In I-COACH, a pseudorandom coded phase mask (CPM) is used to modulate the object wave before its intensity signature is recorded. The imaging process starts with a training stage in which the light diffracted from a point object is modulated by a CPM and a library of point spread holograms (PSHs) for multiple axial locations are stored. A multi-point object placed within the pre-defined axial range is modulated by the same CPM, and the intensity pattern called object hologram (OH) is recorded. The various axial planes of the object are reconstructed by correlating the OH with the corresponding PSHs. In order to remove the bias and background noise generated during cross-correlation between OH and PSHs, multiple intensity patterns are recorded using different CPMs and the intensity patterns are projected into the complex space before the cross-correlation. Further, an averaging technique has been implemented for improving the signal to noise ratio (SNR). Recently, we have shown that I-COACH can retain its lateral resolution capabilities even when most of the light is blocked besides an annular narrow pass along the original aperture [2]. Conventional direct imaging with the same annular aperture fails to preserve the same resolving power, yielding blurred images of the scene. A possible application for the partial aperture configuration has been envisioned with orbiting satellites whose orbital path forms the annular aperture. An aperture ratio (between areas of the ring and the clear circle limited by the ring) of less than 1% is sufficient in the case of I-COACH to reconstruct 3D images of the object with the same lateral resolution as the full clear aperture. However, the averaging technique over images captured with multiple independent CPMs is needed for maintaining a desirable SNR. A total of 60 camera shots were required for every new object in addition to the preliminary training stage involving an additional of 60n camera shots with the point object, where n is the number of the axial positions in the object space. A non-linear reconstruction technique with an improved SNR has been developed lately for 3D imaging by I-COACH with a single camera shot [3,4]. In this study, we implement the non-linear reconstruction procedure in partial aperture imaging to reduce the number of camera shots much below the abovementioned number. In this case, the aperture configuration includes only eight equally spaced isolated subapertures along the orbit. The proposed configuration offers a partial aperture I-COACH with smaller area than [2] and with an improved time resolution due to the use of a single camera shot. Experimental results of the proposed method are compared with the results of direct lens-based imaging.