Rockwell International Corporation

Other

Teledyne Licensing, LLC

The Boeing Company

Rockwell Technologies, Inc.

Quantum Devices, Inc.

William H Southwell

Randolph L Hall

William J Gunning, Iii

Mohsen Khoshnevisan

Kirkpatrick W Norton

Frederick R Vachss

Walter E Johnson

Frank J Woodberry

Joseph Malus

A method is provided for the determination a thickness error in a previously deposited layer using the reflection monitor signal of the currently-depositing layer. This thickness error is then used to compute corrections to the thickness of the currently-depositing layer and the next layer which corrects for the thickness error in the previous layer. The method is stable with respect to noise in the optical monitor signal. The technique is applicable for optical coating designs which are not necessarily quarter wave. The approach avoids the buildup of thickness errors from layer to layer and thus is applicable for very thick designs with many layers. Near the end of a currently depositing layer the monitor signal is used to fit the admittance of the base stack under the current layer. This establishes the parameters in an exact reflectance model used for the thickness monitoring of the current layer.

Optical monitor with computed compensation

This invention describes a means to monitor the deposition of a rugate filter such that the deposited filter will have the specified bandwidth, angular shift properties, and the correct wavelength of the reflectance peak.

Optical monitor for rugate filter deposition

A tunable Fabry-Perot filter that is less sensitive to angle of incidence is formed by replacing the cavity (air gap) with a partitioned cavity that has an effective refractive index greater than one. The partitioned cavity includes a pair of partitioned cavity dielectric layers formed on the reflectors on either side of the variable air gap. Each of the dielectric layers has an optical thickness that is less than one fourth the shortest wavelength in the tuning range of the filter. The resulting three-layer partitioned cavity has an effective optical thickness substantially equal to an integral multiple (m) of one half the transmitted wavelength within the tuning range of the filter.

Partitioned-cavity tunable fabry-perot filter

An optical system employs an optical coating on a substrate positioned relative to an optical collection system. The thickness of the coating is tailored such that light perceived by the collection system over prescribed angles of acceptance has a spectral content that is unchanged, or changed in a prescribed manner, from that entering the system when the sensor is oriented in the 'look ahead' direction. The thickness of the coating is varied so that the wavelengths transmitted or reflected correspond to those required by a specific application. The invention is adaptable to system requirements that are centered about a single wavelength, or that require multiple wavelengths. The optical coating can take any of a number of forms, including stacked dielectric layers and rugate filters.

Optical coating and configuration for tailored spectral characteristics over viewing angle

A complementary comb filter pair, and method for making same, are described, wherein each comb filter element of the complementary pair can be fabricated during the same deposition run. The complementary comb filter is masked so as to retard the thin film growth of the coating, for example, a dielectric material, so as to produce a desired wavelength transmission profile.

Method for the design and fabrication of complementary optical comb filter pairs

An apparatus and method for coupling an array of light beams extending predominantly in one direction into an output port. The light beams are rearranged into a desired shape which extends more equally along two directions than does incident array of light beams. The operation of the rearranging is wavelength insensitive. The rearranged light beams are focused onto the output port. For output ports having a small interface, the focal length of a lens focusing the rearranged light beams to the output port should be as short as possible.

Optical beam coupling of multiple wavelengths into an output channel using spatial wavefront segmentation

A polarizing beamsplitter includes an optical medium and a rugate filter embedded therein. The rugate filter has an average refractive index which varies with position on the rugate plane in the non-thickness direction, where the averaging is across the rugate film in the thickness direction. The variation in the rugate's average index compensates for variations in incident angle across a cone of a divergent light beam. In one embodiment, the period of the rugate is substantially constant across its surface. Most preferably, the amplitude of the rugate index variation has an apodizing amplitude envelope superimposed thereon to aid in coupling the rugate to a surrounding optical medium.

Wide-angle rugate polarizing beamsplitter

A polarizing beamsplitter includes a gradient index film, such as a rugate filter, embedded in an optical medium. The rugate filter is comprises a thin film having a sinusoidal variation in refractive index through its thickness. The embedding medium may include a pair of prisms with the rugate filter between joining faces of the prisms. The rugate filter is embedded so that an incident beam in the embedding medium forms an angle with respect to a normal from the plane of the rugate filter. Embedded at a non-orthogonal angle, the rugate filter is highly transmissive for both the p- and s-polarized broadband components of the incident beam. The beamsplitter is highly reflective, however, at an s-polarization narrow wavelength reflection band determined by the refractive index variations of the rugate filter. Polarizing beamsplitters may be fabricated with multiple reflection bands, including reflection bands in spectral regions other than the visible spectrum. The polarizing beamsplitter can function as a polarizer, a beamsplitter, or a polarizing beamsplitter. An advantage of the invention is efficient reflection of s-polarized light at specific narrow wavelengths with high transmission of s-polarizations at all other wavelengths and p-polarizations at all wavelengths.

Narrow wavelength polarizing beamsplitter

An automotive rear view mirror system comprises passive optical elements (which may include lenses, but must include one or an odd number of mirrors) configured to provide a wide field of view with a negative optical element having a small width dimension mounted externally and close to the body of the vehicle. In a basic embodiment, a small negative optical element, such as a convex mirror, is mounted outside the vehicle, and a larger positive optical element, such as a convex lens, is placed inside the vehicle. The optical elements are positioned to be substantially confocal, with the distance between them equal to the difference in their focal lengths, so as to cancel the curvature of field generated by the external element. The internal element magnifies the image to a size comparable to that obtained with a standard external flat mirror. Alternative embodiments that are optically equivalent may incorporate a more compact 'folding' of the optical path by using at least one additional mirror placed between the external and internal optical elements, thus allowing the elements to be configured more compactly and placed out of the driver's way in the passenger compartment. Because the system does not require a large side-mounted outside mirror as is commonly used on present-day vehicles, the external element may be integrated into the body line of the vehicle to improve aerodynamics, styling, and safety.

Automotive rear view mirror system

A method is provided for monitoring and controlling the deposition of multiple layer thin films using a broadband spectral monitor and a generalized model of the film. A design specification, including the number of layers and the material, refractive index, and thickness of each layer, is provided for the desired thin film. A target optical thickness is computed for the end point of each layer using correction factors based on the generalized model, preferably a single layer model, of the multilayer thin film. A monitor chip, such as a silicon substrate, is used for monitoring the multiple layers of film deposition. During deposition of the film, a broadband spectral monitor (BBSM) comprising a source of broadband light is directed onto the monitoring chip. Light reflected by the monitoring chip is received by a photosensor that provides a broadband reflectance spectrum to a computer. The BBSM reflectance spectrum is fit to the generalized model to produce an output corresponding to the optical thickness of the deposited film. When the broadband spectral monitor optical thickness measurement equals the target optical thickness at the end point of the layer, deposition of that layer is terminated and deposition of the next layer may commence. This process is repeated during the deposition of each successive layer until the entire multiple layer thin film is complete.

Deposition of multiple layer thin films using a broadband spectral

A multiple pass band, thin film optical filter includes a first single pass band filter having a first pass band at a first wavelength, with a first quarterwave stack of thin film layers alternating between layers of a first dielectric material having a first refractive index and layers of a second dielectric material having a second refractive index, the optical thickness of each layer in the first stack being substantially one fourth of the first wavelength. A first half wave layer is interposed within the first stack and has an optical thickness which is an integral multiple of one half of the first wavelength, such that the reflectivities of the portions of the first stack on either side of the first half wave layer are substantially identical. A second single pass band filter having a second pass band at a second wavelength, includes a second quarterwave stack of thin film layers alternating between layers of the first dielectric material and layers of the second dielectric material, the optical thickness of each layer in the second stack being substantially one fourth of the second wavelength, and a second half wave layer interposed within the second stack having a thickness which is an integral multiple of one half of the second wavelength, such that the reflectivities of the portions of the second stack on either side of the second half wave layer are substantially identical. The first and second single pass band filters are combined in series to provide a filter with a pass band at the first wavelength and a pass band at the second wavelength.

Multi-line narrowband-pass filters

A gradient index codeposition process involving refractive index clipping is used to fabricate rugate filters having multiple reflectance bands. During the codeposition process, whenever the superimposed sine wave profiles extend beyond either the upper or lower refractive index limits of the optical materials involved, the index is held at its bound (i.e., clipped). A rugate filter having a multiplicity of stop bands can be fabricated using a rather limited range of refractive index excursions during the codeposition process. Loss of optical density from index clipping can be corrected by a compensating increase in filter thickness.

Multiple line rugate filter with index clipping

A binary optic lens is designed to achieve a predetermined effect on light propagating through the lens by specifying an initial lens design with a plurality of discontinuous subaperture regions, assigning each subaperture region a relative phase difference of 0 or .pi., and calculating the net intensity of light propagating through the lens by coherently summing the wave amplitudes for all of the subaperture regions at a given point in the image plane of the lens. The assigned phase difference for one of the subaperture regions is then changed and the intensity is recalculated by coherently summing the wave amplitudes for all of the subaperture regions at the given point. If the intensity increases over the previously calculated intensity, the changed phase difference is assigned to the selected subaperture region. The steps of changing, recalculating, and assigning are repeated for all of the subaperture regions to make one complete pass through the lens. The entire process is repeated until the calculated intensity no longer increases.

Binary optic lens design using flip-flop optimization

A method is provided for monitoring the refractive index of an optical film as it is being deposited on a substrate. The film is illuminated by a source of light at a wavelength that is outside and less than the reflectance band of the coating. If the refractive index of the film is initially matched to the refractive index of the substrate and has no abrupt changes in its gradient-index profile, reflectance from the surface of the film can be detected and measured. In the absence of interference fringing from internal reflections, surface reflectance of the interface of the film with the surrounding air or vacuum is closely related to the refractive index of the film at its surface. Thus, surface reflection is monitored to provide a control signal to the deposition apparatus to conform the refractive index of material being deposited to a predetermined refractive index profile specified for the desired optical film.

Refractive index monitor for deposition of gradient-index films

A method is provided for monitoring and controlling the deposition of an optical thin film having a refractive index gradient. The optical material to be deposited is evaporated at a controllable rate. In a coevaporation process, evaporation of material having a lower index of refraction is generally held at a predetermined rate while evaporation of material having a higher index of refraction is controllable. During deposition, the film and substrate are illuminated by a broadband light source. The incident light reflected by the film and substrate produces an interference pattern comprising a reflectance spectrum that is detected to compute an optical thickness estimate of the film. The detected reflectance is compared to a reflectance specified for that optical thickness by a predetermined refractive index profile of the desired film. The controllable rate of evaporation is then adjusted so that the refractive index of the material being deposited conforms to the predetermined profile.

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Thousand Oaks, CA, United States of America

William H Southwell