The figure schematically depicts two proposed alternative versions of an instrument that amounts, in effect, to a compact, lightweight optoelectronic microscope that contains no lenses and generates a magnified video image of a specimen. The instrument was described in "Miniature Microscope Without Lenses" (NPO-20218), Vol. 22, No. 8 (August 1998), page 43. In the design and construction of the instrument, the focusing optics of a conventional microscope were replaced by a combination of a microchannel filter and a charge-coupled-device (CCD) image detector. Elimination of focusing optics reduced the size and weight of the instrument and eliminated the need for the time-consuming focusing operation. At the time of the previous article, the instrument was only at the conceptual stage of development, but since that time, a prototype of the instrument has been built and demonstrated to function as intended.

This Miniature Microscope, like its predecessor described in the cited prior article, would not contain any lenses or other focusing optics. Focusing would not be necessary because the microchannels would effect a one-to-one mapping from locations on the specimen to pixel locations on the CCD.

The main differences between the previous version and the present proposed versions of the lensless microscope lie in the manner in which the specimen would be illuminated. The previous version was designed for a partly transparent but highly scattering specimen. The specimen was illuminated in a transmission mode with highly collimated light that was aimed through the specimen parallel to the axes of the microchannels.

According to the present proposal, the specimen would be illuminated in either of two reflection modes. In one case, the illumination would be provided by microscopic light-emitting diodes mounted on the walls between the microchannels, facing the specimen. In the other case, the specimen would be covered by a glass plate. Illumination would be brought in from the side by total internal reflection in the glass plate. A fluid with an index of refraction equal to that of the glass would be placed between the specimen and the glass plate to couple the illumination onto the specimen. There would be a thin airgap between the glass plate and the microchannel plate. Some of the light scattered and reflected by the specimen would travel along the microchannels to the CCD, as in the other versions of this instrument.

This work was done by Yu Wang of Caltech for NASA's Jet Propulsion Laboratory.

NPO-20610

Topics:
Glass Imaging and visualization Light emitting diodes (LEDs) Microscopy Optics Photonics
This Brief includes a Technical Support Package (TSP).
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Reflective Variants of Miniature Microscope Without Lenses

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    Photonics Tech Briefs Magazine

    This article first appeared in the September, 2002 issue of Photonics Tech Briefs Magazine (Vol. 26 No. 9).

    Read more articles from the archives here.

    Overview

    The document presents a technical support package from NASA regarding the development of a miniature microscope that operates without traditional lenses, designed by Yu Wang at the Jet Propulsion Laboratory (JPL). This innovative instrument represents a significant advancement in microscopy, focusing on compactness and efficiency.

    The primary distinction between the previous version of the microscope and the current proposal lies in the illumination method used for the specimen. The earlier design utilized transmission mode illumination, which was suitable for partly transparent but highly scattering specimens. In contrast, the new design proposes two reflection modes for illumination. One method involves using microscopic light-emitting diodes (LEDs) mounted on the walls of microchannels, directing light towards the specimen. The second method employs a glass plate covering the specimen, with illumination introduced from the side through total internal reflection. A fluid matching the index of refraction of the glass is placed between the specimen and the glass plate to facilitate effective light coupling.

    The microscope's design eliminates the need for traditional focusing optics, which reduces its size and weight while also simplifying operation. Instead of lenses, the instrument uses a microchannel filter and a charge-coupled device (CCD) image detector to achieve a one-to-one mapping from the specimen to pixel locations on the CCD. This design not only enhances portability but also streamlines the imaging process, as it removes the time-consuming focusing operation typically required in conventional microscopes.

    The document also emphasizes that the work was conducted under NASA's sponsorship, and it clarifies that references to specific commercial products or manufacturers do not imply endorsement by the U.S. Government or JPL. The prototype of this lensless microscope has been successfully built and demonstrated, marking a significant step forward in the field of microscopy.

    Overall, this miniature microscope without lenses showcases a novel approach to imaging, with potential applications in various scientific fields, particularly where compact and efficient imaging solutions are required. The advancements in illumination techniques and the elimination of focusing optics represent a promising direction for future microscopy technologies.