Browsing by Author "Sharma, Manoj Kumar"

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    Synthetic apertures for long-range, sub-diffraction limited visible imaging using fourier ptychography
    (2020-06-23) Cossairt, Oliver Strider; Holloway, Jason; Veeraraghavan, Ashok; Sharma, Manoj Kumar; Wu, Yicheng; Rice University; Northwestern University; United States Patent and Trademark Office
    A method for imaging objects includes illuminating an object with a light source of an imaging device, and receiving an illumination field reflected by the object. An aperture field that intercepts a pupil of the imaging device is an optical propagation of the illumination field at an aperture plane. The method includes receiving a portion of the aperture field onto a camera sensor, and receiving a sensor field of optical intensity. The method also includes iteratively centering the camera focus along the Fourier plane at different locations to produce a series of sensor fields and stitching together the sensor fields in the Fourier domain to generate an image. The method also includes determining a plurality of phase information for each sensor field in the series of sensor fields, applying the plurality of phase information to the image, receiving a plurality of illumination fields reflected by the object, and denoising the intensity of plurality of illumination fields using Fourier ptychography.
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    WISH: wavefront imaging sensor with high resolution
    (Springer Nature, 2019) Wu, Yicheng; Sharma, Manoj Kumar; Veeraraghavan, Ashok
    Wavefront sensing is the simultaneous measurement of the amplitude and phase of an incoming optical field. Traditional wavefront sensors such as Shack-Hartmann wavefront sensor (SHWFS) suffer from a fundamental tradeoff between spatial resolution and phase estimation and consequently can only achieve a resolution of a few thousand pixels. To break this tradeoff, we present a novel computational-imaging-based technique, namely, the Wavefront Imaging Sensor with High resolution (WISH). We replace the microlens array in SHWFS with a spatial light modulator (SLM) and use a computational phase-retrieval algorithm to recover the incident wavefront. This wavefront sensor can measure highly varying optical fields at more than 10-megapixel resolution with the fine phase estimation. To the best of our knowledge, this resolution is an order of magnitude higher than the current noninterferometric wavefront sensors. To demonstrate the capability of WISH, we present three applications, which cover a wide range of spatial scales. First, we produce the diffraction-limited reconstruction for long-distance imaging by combining WISH with a large-aperture, low-quality Fresnel lens. Second, we show the recovery of high-resolution images of objects that are obscured by scattering. Third, we show that WISH can be used as a microscope without an objective lens. Our study suggests that the designing principle of WISH, which combines optical modulators and computational algorithms to sense high-resolution optical fields, enables improved capabilities in many existing applications while revealing entirely new, hitherto unexplored application areas.
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    WISH: wavefront imaging sensor with high resolution
    (Springer Nature, 2019) Wu, Yicheng; Sharma, Manoj Kumar; Veeraraghavan, Ashok
    Wavefront sensing is the simultaneous measurement of the amplitude and phase of an incoming optical field. Traditional wavefront sensors such as Shack-Hartmann wavefront sensor (SHWFS) suffer from a fundamental tradeoff between spatial resolution and phase estimation and consequently can only achieve a resolution of a few thousand pixels. To break this tradeoff, we present a novel computational-imaging-based technique, namely, the Wavefront Imaging Sensor with High resolution (WISH). We replace the microlens array in SHWFS with a spatial light modulator (SLM) and use a computational phase-retrieval algorithm to recover the incident wavefront. This wavefront sensor can measure highly varying optical fields at more than 10-megapixel resolution with the fine phase estimation. To the best of our knowledge, this resolution is an order of magnitude higher than the current noninterferometric wavefront sensors. To demonstrate the capability of WISH, we present three applications, which cover a wide range of spatial scales. First, we produce the diffraction-limited reconstruction for long-distance imaging by combining WISH with a large-aperture, low-quality Fresnel lens. Second, we show the recovery of high-resolution images of objects that are obscured by scattering. Third, we show that WISH can be used as a microscope without an objective lens. Our study suggests that the designing principle of WISH, which combines optical modulators and computational algorithms to sense high-resolution optical fields, enables improved capabilities in many existing applications while revealing entirely new, hitherto unexplored application areas.