Optical microspectrometer

Details Optical microspectrometer Optical microspectrometer

2002-06-18

2004-05-25

Evans, F. L. (Department: 2877)

Optics: measuring and testing

By dispersed light spectroscopy

Utilizing a spectrometer

Reexamination Certificate

active

06741349

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to optical spectrometers and, in particular, to an imaging optical microspectrometer that uses a grism as the dispersive element and is fabricated lithographically.
BACKGROUND OF THE INVENTION
With the advent of portable, miniature integrated optical systems, there has been an increasing need for microspectrometers that can provide spectral analysis at optical wavelengths. Such microspectrometers have a wide range of potential spectrophotometric applications, including medical diagnostics, wavelength division multiplexing (WDM), and environmental and process analysis.
A particular application of growing importance is for the spectrophotometric analysis of genomic and proteomic microarrays, also termed “DNA chips” or “microchips”. These microchips are used extensively to assess the composition of genetic material in a tissue sample for drug discovery research and are likely also to find application in genetic profiling, medical diagnostics and therapy, and the detection of biowarfare and bioterrorism agents. A typical microchip comprises a checkerboard array of perhaps tens of thousands of different DNA molecules, or probes, tethered to a wafer that can be the size of a microscope slide. Genetic material that carries a fluorescent tag, or label, selectively reacts with the DNA molecules on the microchip. The fluorescence from the dye-tagged microchip can then be scanned to provide a color-coded readout of the microarray to determine gene activity.
A planar grating microspectrometer has been developed, primarily for WDM applications. Anderer et al. “Development of a 10-channel wavelength division multiplexer/demultiplexer fabricated by an X-ray micromachining process” SPIE 1014, 17 (1988). A later version of this planar grating microspectrometer is marketed by Steag microParts. See “Optical Devices: Microspectrometers,”[retrieved on May 9, 2002]. Retrieved from the Internet:<URL:http://www.microparts.de/english/optics. html>. The commercial microspectrometer comprises a monolithic dielectric slab waveguide with an integrated focusing echelette grating formed on the convex edge of the waveguide by a micromolding technique. Light is injected into the waveguide, dispersed by the grating, and focused into ten output optical fibers. The microspectrometer has a spectral range of 380 nm-780 nm and a numerical aperture of about 0.2 with a 50/125 &mgr;m optical input fiber. The microspectrometer itself has a footprint of about 29×14 mm
2
. Another microspectrometer uses a planar waveguide with a selffocussing phase transmission grating in a compact rectangular design with a footprint of 11×11 mm
2
. Sander et al., “Selffocussing phase transmission grating for an integrated optical microspectrometer”,
Sensors and Actuators
A88, 1 (2001).
Neither of these planar microspectrometers is suitable for two-dimensional imaging of a planar object. Also, these planar microspectrometers have a relatively large footprint and cannot easily be fabricated into a microspectrometer array.
The optical microspectrometer of the present invention can spectrally image a line object. A single optical microspectrometer can be used to sequentially scan a planar object, such as a dye-tagged microchip. Because the optical microspectrometer is very compact, multiple optical microspectrometers can be arrayed to provide simultaneous readout of the planar object. The optical microspectrometer can be used to identify dye tags and for coarse WDM. The present invention uses a lithographic process, such as deep X-ray lithography (DXRL), to provide for the monolithic fabrication of the pre-aligned microoptical elements of the optical microspectrometer on a common substrate.
SUMMARY OF THE INVENTION
An optical microspectrometer for spectral imaging of light from an object comprises a substrate having a surface with a plurality of microoptical elements monolithically formed thereon and aligned on an optical axis, the microoptical elements comprising a slit through which the light from the object passes, a collimating lens to collimate the light from the slit, a grism to disperse the collimated light from the collimating lens, and an imaging lens to focus the dispersed light from the grism and provide a spectrally resolved image of the slit on a detector. The microoptical elements can further comprise a collecting lens to collect light from the object and a focusing lens to focus the collected light from the collecting lens onto the slit.


REFERENCES:
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patent: 6249346 (2001-06-01), Chen et al.
patent: 6496616 (2002-12-01), Frish et al.
Anderer, et al., “Development of a 10-Channel Wavelength Division Multiplex/Demultiplexer Fabricated by An X-Ray Micromachining Process,”Proc. SPIE Micro-Optics 1014, 17 (1988).
Mohr, et al., “Fabrication of a Planar Grating Spectrograph by Deep-etch Lithography with Synchrotron Radiation,”Sensors and Actuators A 27, 571 (1991).
Staerk, et al., “Design considerations and performance of a spectro-streak apparatus applying a planar LIGA microspectrometer for time-resolved ultrafast fluorescence spectroscopy,”Rev. Sci. Instrum. 67(7), 2490 (1996).
Capron, et al., “Design and Performance of a Multiple Element Slab Waveguide Spectrograph for Multimode Fiber-Optic WDM Systems,”J. Lightw. Technol. 11(12), 2009 (1993).
Sander, et al., “Microspectrometer with slab-waveguide transmission gratings,”Appl. Optics 35(21), 4096 (1996).
Sander, et al., “Selffocussing phase transmission grating for an integrated optical microspectrometer,” Sensors and Actuators A 88, 1 (2001).
Steag microParts, “Optical Devices: Microspectrometers,” [retrieved on Jun. 13, 2002]. Retrieved from the Internet:<URL:http://www.microparts.de/english/optics.html.

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