In a proposed optical microscope, the focusing optics of a conventional microscope would be supplanted by a combination of a microchannel filter and an advanced electronic image sensor. Elimination of focusing optics would eliminate the need for the time-consuming focusing operation, making it possible to examine different specimens in faster succession. Elimination of the focusing optics would also result in a smaller, lighter instrument.
Electronic image sensors with pixel sizes of several microns have been developed. During the next few years, pixel sizes in advanced image sensors may be reduced to < 1 μ m - close to the limit of resolution of a conventional microscope with focusing optics. In that case, and if it were possible to effect a one-to-one mapping from a point on a specimen to a pixel in such an image sensor, then the electronic output of the sensor would contain image information equivalent to that from a microscope.
The desired one-to-one mapping could be obtained by use of conventional optics to focus an image of the specimen onto the image sensor, but in this case, one seeks to avoid the use of focusing optics. Instead, according to the proposal, the following would be done: The specimen would be illuminated with highly collimated light (e.g., laser light) aimed through the specimen and toward the image sensor (see figure). Assuming that the specimen were thin enough to be partially transparent but were also highly scattering, the unscattered portion of the incident light would continue to travel along the direction of incidence, and some would be scattered in other directions.
A narrow-angle filter - a filter capable of absorbing the scattered light - would be placed between the specimen and the sensor. Such a filter could be constructed as a plate or block of opaque material with straight microchannels; more specifically, parallel microscopic-cross-section holes much longer than they are wide. The microchannels should be positioned and dimensioned so that each one is registered with a pixel on the image sensor.
The scattered light would be absorbed on the walls of the holes, and only the unscattered light would pass through. Therefore, the light arriving at each pixel on the sensor would have traveled along a straight line from a corresponding location on the specimen. Given the parallelarity of the holes and of all the optical paths in a collimated beam of light, the geometric relationship among the pixels would match that of the corresponding location in the specimen. Thus, the desired one-to-one mapping would have been effected.
This Miniature Microscope would not contain any lenses or other focusing optics. Focusing would not be necessary because the specimen would be imaged in collimated light on an electronic image sensor with microscopic pixels.
This work was done by Yu Wang of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Physical Sciences category.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
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Refer to NPO-20218, volume and number of this NASA Tech Briefs issue, and the page number.
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Miniature microscope without lenses
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Overview
The document discusses a novel optical microscope design developed by Yu Wang at NASA's Jet Propulsion Laboratory, which eliminates traditional focusing optics in favor of a microchannel filter combined with an electronic image sensor. This innovative approach addresses the limitations of conventional microscopes, which have remained largely unchanged for over a century and require time-consuming focusing adjustments each time a new specimen is examined.
The proposed microscope utilizes highly collimated light, such as laser light, directed through a specimen that is thin enough to be partially transparent but highly scattering. The unscattered light continues in the direction of incidence, while scattered light is absorbed by the walls of a narrow-angle microchannel filter positioned between the specimen and the image sensor. This filter consists of parallel microscopic channels that allow only the unscattered light to pass through, effectively creating a one-to-one mapping from the specimen to the pixels of the image sensor.
As electronic image sensors have advanced, pixel sizes have decreased to several microns, with future developments expected to achieve sizes below one micron. This reduction in pixel size approaches the optical resolution limit of conventional microscopes, making it feasible to capture high-resolution images without the need for focusing optics. The design's compactness and lightweight nature make it particularly suitable for applications where portability is essential, such as in space exploration or fieldwork.
The document highlights the advantages of this miniature microscope, including its ability to handle large volumes of samples quickly and efficiently, as well as its potential for high-resolution imaging. The elimination of focusing optics not only simplifies the operation but also reduces the overall size and weight of the instrument, making it more user-friendly.
In summary, this innovative microscope design represents a significant advancement in optical imaging technology, offering a practical solution to the challenges posed by traditional microscopes. By leveraging microchannel filters and advanced electronic sensors, it promises to enhance the speed and efficiency of specimen examination while maintaining high image quality. This work is part of ongoing efforts to improve scientific instrumentation for various applications, including those in space research.
