Spectrally Shaped Light Source

A spectrally-shaped source includes a source that generates a round beam. An optical element transforms the round beam to a rectangular beam. An image forming dispersive device angularly disperses wavelengths and images the rectangular beam at a modulation plane. A pixelated SLM is illuminated by the dispersed wavelengths of the rectangular beam such that each column of illuminated pixels is illuminated by a different wavelength. Toroidal optics projects light directed from the SLM to an output plane and focuses the angularly dispersed wavelengths of the beam so that a selected portion of the optical beam is reflected toward the toroidal optic by the SLM. A controller instructs the pixelated SLM to selectively reflect the portion of the optical beam toward the toroidal optic and to selectively reflect another portion of the beam away from the toroidal optic so as to provide a desired spectral shape.

INTRODUCTION

Numerous commercial and academic applications have need for high brightness light over a broad wavelength range. For example, laser-driven light sources are available that provide high brightness over spectral ranges from the extreme UV through visible and into the infrared regions of the spectrum with high reliability and long lifetimes. Various types of such high-brightness light sources are commercially available from Energetiq, a Hamamatsu Company, located in Wilmington, Mass.

The widespread availability of high-brightness light sources, together with growing applications that use high brightness light, has driven the need for systems that shape the spectrum of the optical output of the high-brightness light source. Spectral shaping systems are needed that can provide, for example, specific wavelength distributions. This includes systems that can provide nearly arbitrary shapes of the output spectrum from UV to infrared and also enable programmable and controllable wavelength spectrums of light at an output.

SUMMARY

The present teaching relates to spectrally shaped sources that shape the spectrum of light generated by a high-intensity broadband light source to provide a high-brightness output optical illumination with a desired spectrum. More specifically, the present teaching relates to various embodiments of a high-intensity broadband light source that produce a round-shaped optical beam that is transformed by an input optical element into a rectangular shaped optical beam. An imaging dispersive optical element angularly disperses the wavelengths of the rectangular optical beam in one dimension and images the rectangular optical beam to illuminate a pixelated Spatial Light Modulator (SLM). Selective reflection of the pixelated spatial light modulator illuminated by the dispersed imaged optical beam produces various desired intensities of spectral output in a particular reflected direction towards a toroidal mirror.

In some embodiments of apparatus according to the present teaching, each column of an array of pixels in the pixelated spatial light modulator is illuminated at the same height by a different wavelength in the optical beam. Each column of the array of pixels in the spatial light modulator array that is illuminated is controlled to selectively reflect a desired portion of the light illuminating each column to the toroidal mirror. The toroidal mirror serves to simultaneously focus in the dispersion direction and image the rectangular shaped optical beam at an output plane. This action of the toroidal optic results in the selected portions of the dispersed wavelengths that are reflected toward the toroidal optic being overlapped in an image of the rectangular shape at an output port of the spectrally shaped source, and thus provides output optical illumination comprising a desired spectrum at the output port.

One feature of the spectrally shaped source of the present teaching is that it exhibits very high optical efficiency and can be constructed to be easy to assemble and physically compact. In addition, the spectrally shaped source generates a desired output spectrum that has high resolution and high precision and accuracy. More specifically, the use of a transformed rectangular shape optical beam of the present teaching has at least three key advantages over known systems. First, it improves a resolution of the spectral selectivity of the spectral shaper, much like a slit is used to improve a resolution of a spectrometer. Second, the rectangular shape simplifies the operation of the pixelated spatial light modulator because the modulator is illuminated by rectangular shaped images of the input beam that are separated in wavelength by the dispersive device. Thus, only a height of the illuminated columns of the array needs to be determined to provide a desired intensity of a reflected portion of an optical beam of a given wavelength. Third, the rectangular shape improves the integrity of the provided spectral profile because each reflected portion of a particular wavelength in the spectrum is independent of another reflected portion. In various embodiments, different lengths and positions for the selected portion of the pixel column that are chosen to reflect the optical illumination are used.

The spectrally shaped source of the present teaching includes optical elements positioned so as to support appropriate orientation and position of the various input and output planes as well as the plane of the spatial light modulator for various features, such as compact design, ease of assembly, high resolution, high precision, and high accuracy of spectral output. Various shapes and numbers of pixels, in one or more columns, can be controlled to reflect the portion of the optical beam to the toroidal optic to provide tailoring of the spectrum of the output illumination. Also, a spectral extension source can be optionally coupled to the output of the spectrally shaped source to expand the output spectrum wavelength range of the optical signal. The spectral extension source can be a light emitting diode (LED). The spectral extension source can also be a NIR LED. In addition, a fiber bundle can be used to transform the optical beam shape to provide a highly accurate beam shape with low loss. In addition, optical elements are positioned such that the toroidal optics configuration accommodates “off-axis” mirrors, i.e. 45-degree axis, for Digital Light Processing (DLP) micro-mirror embodiments. Furthermore, various techniques can be employed to provide stray light suppression.

DESCRIPTION OF VARIOUS EMBODIMENTS

Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the teaching. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

It should be understood that the individual steps of the method of the present teaching can be performed in any order and/or simultaneously as long as the teaching remains operable. Furthermore, it should be understood that the apparatus and method of the present teaching can include any number or all of the described embodiments as long as the teaching remains operable.

FIG. 1illustrates a system diagram of an embodiment of a spectrally shaped source100according to the present teaching. A high intensity optical source102produces high-brightness light at an output. The optical source102can be, for example, a high-brightness laser driven light source (LDLS), such as a laser driven xenon lamp, that provides broadband light supplied by a high-intensity plasma at an output. The source102can also be, for example, a super continuum fiber laser.

The output light is collected by input optics104and directed to an image forming grating106. The image forming grating106in some embodiments is an image forming dispersive device. The input optics104can include various optical elements including, for example, bulk optical components and/or fiber optic components. The input optics104can transform the spatial output of the light from the source102into a desired spatial profile at an input plane of the spectral shaper system108. The image forming grating spatially separates the wavelengths of the light from the input and directs the light to a spatial light modulator110.

The spatial light modulator110modulates the light in the spatially separated wavelengths of light independently and directs them to a toroidal optic element112. In some embodiments, the spatial light modulator is a pixelated spatial light modulator. In some embodiments the pixels form a one-dimensional array. In some embodiments, the pixels form a two-dimensional array. In some embodiments, the pixelated spatial light modulator110comprises a digital micro-mirror device (DMD). In some embodiments, the pixelated spatial light modulator comprises a liquid crystal on silicon (LCOS) device. Also, in some embodiments, the pixelated spatial light modulator110includes an order-sorting filter that increases spectral purity.

The toroidal optic element112directs the light reflected toward the toroidal optical element112by the spatial light modulator110to output optics114. The toroidal optic element112collects and focuses light from the spatial light modulator110. Some embodiments of the toroidal optic element utilize a reflective surface with a toroidal shape that recombines the spatially separated wavelengths of light and images the light from the surface of the modulator that are directed to the toroidal optic to an output plane. The output optics114can include various optical elements including, for example, bulk optical components and/or fiber optic components and can be used, for example, to couple the imaged optical light into an optical fiber or other lightguide.

A controller116is connected to the high-intensity light source and/or the spatial light modulator110to control the modulation of the light to provide a desired optical spectrum at the output of the output optics114. In some embodiments, the controller116operates in an open-loop configuration, and uses, for example, pre-loaded spectrum files to determine how to control the spatial light modulator. For example, the pre-loaded spectrum files can include how many pixels in a column of the modulator110associated with a particular wavelength are directing light toward the toroidal optical element112. In these embodiments, no external sensor and/or spectrometer is needed to adjust the spectral profile. This feature is possible because of the precise shaping and spectral imaging of the optical beams in the system. The input beam and the image forming grating106are configured to illumination a precise shape and size of a region on the modulator with a particular desired wavelength. Because of the precise illumination region size and shape, the number and position of pixels illuminated by the desired wavelength in the region can be determined. A pixel in the “on state” reflects light, while a pixel in the “off state” does not reflect light. Therefore, the intensity of light reflected from the region is controlled by controlling the number of pixels in the “on state”. Thus, it is possible to produce a desired intensity of a particular wavelength at the output only by controlling the number of pixels in the “on state” in the illuminated region. In some embodiments, the size and shape of the image beam is a rectangular shape that illuminates one column of a two dimensional array of pixels in the modulator.

Various embodiments of the spectral shaper system108may or may not include specific input optics104or output optics114, depending on the application. Some embodiments of the spectral shaper systems108can include an internal controller with pre-loaded control algorithms for controlling the spatial light modulator to provide desired spectral shapes of the output light.

One feature of the present teaching is that the spectrally shaped source100can include input optics104that spatially shape the high-brightness light from the optical source102to provide a spatial profile at an input plane of the shaper that produces a desired image at the plane of the spatial light modulator110after transformation by the image forming grating106. For example, in some embodiments, it is desirable that the spatial profile of light at an input plane of the shaper optical system108have a substantially rectangular shape. The light that emerges from the high-brightness source102can be, for example, generally a circular shape. Thus, in some embodiments, the input optics104performs a transformation from a circular shape input to a rectangular shape output.

FIG. 2Aillustrates a schematic of some elements200including the input optics202and light source204for an embodiment of a spectrally shaped source according to the present teaching. The light source204generates light from a high-intensity plasma206that diverges from the light source204. Focusing optics208in the input optics202collect the divergent light from the light source204and focus the light to an input of an optical fiber bundle210. In some embodiments, the fiber bundle210is configured to transform a shape of the focused beam that is coupled at the input of the fiber to a desired output shape.

FIG. 2Billustrates an input cross section230of an embodiment of a fiber bundle210for a spectrally shaped source according to the present teaching. Individual fibers232in the bundle are arranged in a nominally circular shape at the input.

FIG. 2Cillustrates an output cross section of an embodiment of the fiber bundle210for a spectrally shaped source according to the present teaching. Individual fibers232in the bundle are arranged in a nominally rectangular shape at the input. In this embodiment, that shape is provided by a single column of 24 fibers. Other embodiments can use different aspect ratios of height-to-width of the rectangular shape and/or different numbers of fibers. The transformation from circular shape to rectangular shape is achieved by rearranging the positions of the fibers232over the length of the bundle210to realize the desired shape transformation. As understood by those skilled in the art, numerous shapes and shape transformations can be achieved using a fiber bundle. In some embodiments, a shape of an input cross-section of the fiber bundle is provided that closely matches an image of a plasma206or other light-generating element in the source204. In some embodiments, a shape of the output cross-section of the fiber bundle210is provided that has a rectangular shape that is matched to a shape of a pixel, or group of pixels, in the spatial light modulator in the shaper system.

FIG. 3illustrates a perspective view of an embodiment of part of a spectral shaper system300that includes the input fiber plane302, image forming dispersive device304, and spatial light modulator plane306of a spectrally shaped source according to the present teaching. A length scale310is indicated. This length scale310is exemplary and shaper systems of the present teaching are not limited to this size or shape as understood by those skilled in the art.

Input light, which can be white light or other broadband light, is introduced into the shaper as an optical beam308having a particular shape. The shape may be provided by passing the optical beam308through a fiber array. While a fiber array is described herein, other input optics can be used to provide an input optical beam308with a desired shape at the input plane302. The fiber array can be, for example, a straight-line fiber-array or a rectangular array or other shape. In some embodiments, the fiber array is a straight-line fiber-array constructed from a multi-strand fiber bundle with a circular input bundle cross-section and a straight-line output end. In some embodiments, the light from the array is formed in a shape of a rectangular optical beam308.

The light in the optical beam308from the array is then directed to the image forming dispersive device304that separates the spectrum of the light in the shaped optical beam into spatially separated beams. Thus, the image forming dispersive device304angularly disperses wavelengths of the optical beam in a dispersion direction and images the shape of the optical beam at a modulation plane306. In some configurations according to the present teaching, the optical beam is formed in a rectangular shape. In some embodiments, the image forming dispersive device304is a concave, aberration-corrected, image-forming grating. The use of a curved dispersive element to image the input optical beam can eliminate the need for an extra optical element, such as a lens, needed in the shaper system to perform the imaging.

The image forming dispersive device304produces an image of the fiber-array308output at the input plane302onto a surface of a spatial light modulator (not shown) positioned in a modulator plane306. Different wavelengths of light separated by the dispersive device304are separately imaged onto different modulator regions. In some configurations according to the present teaching, the input light is a rectangle shape and modulator regions are columns of an array of pixels that form the modulator. For example, for an individual wavelength of input light, the dispersive element forms an image of the input light beam shape onto a specific column of a modulator.

For a broadband light input, images of the input shape at different wavelengths are formed on different columns of the pixelated modulator, forming a rainbow across the columns. In some embodiments, the modulator is a DMD modulator, and the different wavelength images coincide with different micro-mirror pixel columns. Various descriptions herein will refer to particular rows and/or columns of pixels as representing one dimension of the array without loss of generality, as the relative orientation of the array is arbitrary as understood by those skilled in the art.

In some embodiments, the input plane302and the modulator plane306are different planes, and a normal to the input plane302is not collinear with a normal to the modulator plane306. This configuration assists in providing a compact three-dimensional package for the optical system, which maintains a high-quality image of the optical input shape at the modulator plane306.

FIG. 4illustrates another perspective view of the embodiment of the spectral shaper system400including the input fiber plane302, image forming dispersive device304, and spatial light modulator plane306for the spectrally shaped source ofFIG. 3. The length scale310is also shown. The fiber array308and modulator312are shown. This view shows the three surfaces of the array, a view at the input plane302, a view at the concave surface of the dispersive device304that spreads the individual wavelengths in space to form images at different wavelengths, and a view at the plane306of the input to the modulator312. Each wavelength that emerges at a different angle from the dispersive device304forms a separate image of the input array308in different regions of the modulator312based on the wavelength separation provided by the grating and the curvature of the dispersive device304. In some embodiments, the dispersive device304also provides correction for spherical aberration.

In some embodiments, an order-sorting filter is positioned in the path between the image forming dispersive device304and the modulator312. The order-sorting filter can be positioned on or integrated into the image forming dispersive device304and/or the modulator312. The order-sorting filter enhances the spectral purity of the spectrum in the image plane by rejecting the second-order of shorter-wavelength light from mixing with the first-order light. The first and second orders have a wavelength difference of a factor of two. For example, a 400 nm second order wavelength is rejected and will not overlap with the 800 nm first order wavelength of light.

FIG. 5illustrates another perspective view of the embodiment of the spectral shaper system500including the input fiber plane302, image forming dispersive device304, spatial light modulator plane306, toroidal mirror314, and output optics316for the spectrally shaped source ofFIG. 3. The length scale310is also shown. The system includes the fiber array308and the modulator312shown inFIG. 4. A toroidal mirror314and output optics316, which in this embodiment is a lens, are used to project the optical light directed from the modulator312to the toroidal mirror314to an output plane318of the shaper system500. The modulator312is controlled to direct light from some regions of the modulator312toward the toroidal mirror314while directing light from other regions of the modulator312away from the toroidal mirror314. For example, in some embodiments, light from one or more pixels of a DMD is directed toward the mirror314and light from other pixels is directed away from the mirror314.

In some embodiments, the modulator312is a two-dimensional array of pixels comprising rows and columns of pixels. Light from a rectangular shaped optical beam at the input plane312is imaged such that a width and height of the imaged rectangle at the modulator plane306corresponds to a width and height of a column of pixels. The spatial separation of wavelengths by the dispersive device304causes different wavelengths of light to illuminate different columns of pixels. A controller (not shown inFIG. 5) is used to configure each of the pixels in the modulator312to direct light toward or away from the toroidal mirror314.

The dispersive device304configuration determines the central wavelength and spectral bandwidth around the central wavelength, which can be referred to as a spectral segment, that is directed to each column of pixels in the modulator312. A certain fraction of the pixels in a column are then controlled to direct the light to the mirror314, while the remaining pixels direct light away from the mirror314. Different columns correspond to different spectral segments of light. In this way, a controlled fraction of the intensity of light in a particular spectral segment that is directed to the mirror314is then reflected by the mirror314to the output, thereby providing a controlled intensity of light in the spectral segment at the shaper output. Because different spectral segments associated with different columns are independently controlled, this feature provides a controlled shape of the intensity as a function of wavelength at the shaper system output.

One feature of using the rectangular shape of the optical light at the input plane302as described is that a very low loss, or high throughput efficiency can be realized. This occurs because the image efficiently illuminates the surface of a rectangular modulator312so nearly all the input light impinges to a pixel and nearly all light directed by the modulator to the toroidal mirror314appears at the output plane318. Also, high accuracy of intensity is provided because the pixels are uniformly illuminated. It should be understood that in various embodiments, different shapes of image from the input plane302to the modulator plane306, as well as different shapes of illuminated regions on the modulator312, are also possible.

One feature of the present teaching is that the image formed by the image forming dispersive device304of the rectangular shaped input optical beam illuminates the pixels in columns of the modulator312at a uniform height. In this case, a height of pixels in a column associated with a particular wavelength that are controlled to reflect the light from the surface of the modulator312toward the toroidal mirror314determines the fraction of the illumination in that wavelength that appears at the output. Controlling the various heights of the columns of the pixels in the modulator then provides a desired spectral shape of the illumination at the output plane318.

Also, the amount of light reflected toward the toroidal mirror in a given wavelength band associated with a column of the spatial light modulator312can be determined by a number of pixels in that column that are controlled to direct light to the toroidal mirror314. Thus, in some embodiments, a number of pixels in at least one column of pixels that is illuminated by the angularly dispersed wavelengths of the rectangular optical beam imaged by the image forming dispersive device is chosen to provide a desired spectral shape of the output optical illumination at the output plane318.

The toroidal mirror314is configured with a reflective surface in a shape that spatially recombines the wavelengths from the spatial light modulator312that are directed to the surface of the mirror314and direct them to the output optics316. The output optics316couple the spatially recombined light into a desired receiving optical system (not shown) positioned at an output plane318of the shaper system500. The output optics316in some embodiments is an output lens that couples the output light directed off of the toroidal mirror314to a liquid light guide (not shown). Other optical systems for receiving the optical beam from the output plane318are also possible as can be based on a particular application.

FIG. 6illustrates another perspective view of the spectral shaper system600including the input fiber plane302, image forming dispersive device304, spatial light modulator plane306, toroidal mirror314, and output optics316of the spectrally shaped source ofFIG. 3. This view of the shaper system600illustrates an optical axis through the input plane302to the dispersive device304and how the dispersive device304directs the light to the modulator plane306with a normal that is non-collinear with the optical axis through the input plane302to the dispersive element304. This view of the shaper system600also shows how the toroidal mirror314has a three-dimensional toroidal surface shape that both spatially recombines the wavelengths that are directed toward the mirror314and directs them towards the output plane318.

The embodiment of the spectral shaping system shown inFIGS. 3-6is illustrated with the dispersive device, modulator, and toroidal optical elements configured as reflective devices. It should be understood that one or more of those elements can be configured as a transmissive device with well understood modifications to the optical system and still be consistent with a spectral shaper system of the present teaching.

One feature of the spectral shaping system of the present teaching is that it can be designed to accommodate multiple wavelength ranges of interest. For example, embodiments of the system operate over a wavelength range from ˜380 nm to ˜760 nm. This may be referred to as the UV and visible region of the spectrum. Embodiments of the system also operate over a wavelength range from ˜380 nm to ˜1100 nm. This extended wavelength range includes spectral components in the near infrared (NIR) region of the spectrum, nominally from ˜760 nm to ˜1100 nm.

Some embodiments of the spectral shaper according to the present teaching produce spectral shaping in the NIR region of the spectrum that share the image-forming dispersive element and modulator, but have different input configurations for the UV and/or visible light and the NIR light. These embodiments locate the shaped optical beam in the NIR region of the spectrum at a position that generates astigmatism aberrations from the image forming dispersive device, and then these aberrations are used to locate the NIR spectrum at a different position on the surface of the spatial light modulator from the visible/UV spectrum. Thus, the NIR spectral components and visible and/or UV components can be independently controlled because they illuminate different pixel columns.

FIG. 7Aillustrates a perspective view of an embodiment of a spectral shaper system700including the input planes702,704, image forming dispersive device706, and spatial light modulator plane708of an infrared-extended spectrally shaped source according to the present teaching. The shaper system700shown in perspective view700has a length scale711indicated. This length scale710is exemplary and NIR-extended shaper systems of the present teaching are not limited to this size or shape as understood by those skilled in the art.

Visible and/or ultraviolet input light is introduced into the shaper system700as an optical beam having a rectangular shape at the visible input plane702. In some embodiments, the visible light is a line shape. Near infrared light is input at a NIR input plane704. In some embodiments, the NIR light is input as a point source shape. The light from the visible input plane702and the light from the NIR input plane704is directed to the image forming dispersive device706. The image forming dispersive device706separates the spectrum of the light in the shaped optical beams from the NIR and visible planes702,704into spatially separated beams and directs them to the spatial light modulator window710positioned at a spatial light modulator plane708such that the NIR spectrum is parallel to the visible spectrum on the modulator712positioned just behind the window710. The NIR subsystem shares the same optical path with the visible system. In some embodiments, the visible light is provided by a fiber bundle with a linear array of fibers at the output cross section. This produces a line shape. In some embodiments, the NIR system is nominally a point source. This point source can be provided, for example, from a single optical fiber output.

The NIR shares this path until it is coupled into an output optical device, which may be a liquid light guide. Both of the visible and NIR spectra are located on the spatial light modulator with a spatial gap, so they can be independently manipulated by the spatial light modulator712and controller (not shown). In this embodiment, the NIR input is offset from an optimum input position that would have no aberration. The offset position introduces astigmatism from the image forming dispersive device706, which serves to generate a line shape of NIR light at the spatial light modulator712from the point source shape of the NIR input light. The aberrations also serve to locate the NIR spectrum at a different position from the visible light on the modulator712. In contrast, the visible input, which is a line source shape is imaged with no aberration.

Similar to the embodiment described in connection withFIG. 3, the image forming dispersive device706of the embodiment ofFIG. 7Aproduces an image of the shaped optical beam at the visible input plane702and the NIR input plane704at the modulator plane306(FIG. 3). Different wavelengths of light separated by the dispersive device706are separately imaged onto different modulator pixel regions. In some embodiments, the modulator is a DMD modulator, and the different wavelength images coincide with different DMD pixel columns. In some embodiments, the input planes702,704and the modulator plane708are different planes, providing a compact three-dimensional package for the optical system. Optionally, an optical wedge714can be used to project the NIR optical beam, and an optical aperture716can be used to aperture the visible and/or UV optical beam from the input planes702,704.

FIG. 7Billustrates another perspective view730of the spectral shaper system for an infrared-extended spectrally shaped source ofFIG. 7A. The length scale711is shown. This view730shows the visible input plane702and the visible line source optical beam that enters the system at that plane702. The NIR optical beam input is a point source at the NIR plane704that passes through the optical wedge714. The NIR light passes an aperture724and the visible light also passes and aperture716and then both beams impinge the image-forming dispersive device706. The image-forming dispersive device706spatially separates the wavelengths of light of both the visible and NIR light. The image-forming dispersive device706images different color points of light from the NIR light and different colored lines of light from the visible light to the spatial light modulator712after passing through the window710.

A controller (not shown) is used to control the spatial light modulator712such that a desired amount of light from each color is directed to the toroidal mirror718that spatially recombines the wavelengths and directs the desired amount of light from each color to a collection lens720. The collection lens provides an optical beam at an output plane722with a desired spectral shape of the output optical illumination.

FIG. 7Cillustrates a portion of yet another perspective view of the spectral shaper system750for the infrared-extended spectrally shaped source ofFIG. 7A. The visible input plane702, NIR input plane704, image forming dispersive device706, spatial light modulator plane708, spatial light modulator window710, spatial light modulator712, toroidal optical mirror718, collection lens720, and output plane722are shown. The scale711is indicated. This view of the spectral shaper system750illustrate the complex three-dimensional trajectories of the optical beams that pass through the system. This is why a toroidal mirror718is needed to both spatially recombine the wavelengths dispersed by the dispersive device706and to re-image the light at the output plane722.

FIG. 8Aillustrates the illumination800of a modulator802showing the illumination from the visible spectrum804and the NIR spectrum806of a spectral shaper system of the present teaching. A length scale801is provided. The light from the visible spectrum804and the NIR spectrum806share the same modulator802. The visible light804impinges the top half of the modulator802, and exhibits high resolution due to lower aberrations from the imaging dispersive device. The NIR light806impinges on the bottom half of the modulator802and exhibits lower resolution due to aberration in the imaging dispersive device. Thus, the two spectra804,806are spatially separated and there is only minimal wavelength range overlap. In some embodiments, bandpass filters are used.

FIG. 8Billustrates the illumination850of the modulator regions852,856from a face-on view of the system ofFIG. 8A. A wavelength scale856is shown, with different wavelengths of light having different symbols and different grey scale levels in the simulation in the regions852,854. In the NIR spectrum region854, for each wavelength, the spectral lines860are tilted and parallel with the spectral lines of other wavelengths. As a result, the output for the NIR is a line image when these lines are recombined in the toroidal mirror. The visible light858has higher resolution, and the input array shape is imaged on the modulator802and also at the output of the shaper system after being recombined in the toroidal mirror. Note that although individual circular array elements from a linear array of optical fibers provided at the input are resolved as three individual spots, such a pattern can be referred to as a line shape or a rectangular shape. Generally, in connection with the apparatus according to the present teaching, the visible spectrum804covers a range from ˜380 nm to ˜750 nm, and the NIR spectrum806covers a range from ˜700 nm to ˜1100 nm.

FIG. 9Aillustrates a simulation of the spatial distribution900of an output beam spot in the near-infrared region of the spectrum of an embodiment of the spectral shaper system of the present teaching. The grid squares902are one-millimeter square. The legend904refers to the grey scale in the figure which shows different wavelengths from 0.7 micrometers to 1.1 micrometers. The spatial distribution900represents the spot size at the input surface to, for example, an output liquid light guide coupled to the shaper system (not shown).

FIG. 9Billustrates a simulation of the spatial distribution930of an output beam spot in the visible region of the spectrum of an embodiment of the spatial shaper system of the present teaching. The grid squares932are one-millimeter square. The legend934refers to the grey scale representing different wavelengths from 0.38 micrometers to 0.75 micrometers. The spatial distribution930represents the spot size at the input surface to, for example, an output liquid light guide coupled to the shaper (not shown).

FIG. 9Cillustrates a simulation of the composite spatial distribution950of an output beam spot in the near-infrared and visible regions of the spectrum of the embodiment of the spatial shaper system ofFIGS. 9A and 9B. The grid squares952are one-millimeter square. The legend954refers to the grey scale in the figure representing different wavelengths from 0.38 micrometers to 1.0 micrometers. The spatial distribution950represents the spot size at the input surface to, for example, an output liquid light guide coupled to the shaper system (not shown). This result is achieved with visible and NIR that share the same optics in the spectral shaper system. The output of the shaper system has the visible and NIR light overlapped onto a small area. The area has a dimension of approximately four millimeters by five and a half millimeters. This size and shape of a spatial distribution950at the output plane of the spectral shaper can be efficiently collected by a liquid light guide.

FIG. 10Aillustrates the results of a Zemax™ model simulator output1000of the modulator plane in an embodiments of a near-IR extended spectral shaper system of the present teaching. The NIR region1001of the modulator shows illumination patterns1002,1004,1006,1008,1010for five different individual NIR wavelengths with a line shape that is slightly tilted as a result of some aberration in the imaging dispersive element because of the offset placement of the input NIR point source at the NIR input plane. The visible region1011of the modulator shows illumination patterns1012,1014,1016,1018,1020for five different individual visible wavelengths with a higher-resolution image of a three-element linear fiber array input at the visible input plane, as imaged by the imaging dispersive element with aberration correction. The Model1000shows a clear gap between individual NIR spectral images1002,1004,1006,1008,1010and visible images1012,1014,1016,1018,1020.

FIG. 10Billustrates photographs1030,1050of the modulator plane for two measurements of embodiments of a near-IR extended spectral shaper system of the present teaching. The NIR regions1032,1052and the visible regions1034,1054of the modulator for each photograph1030,1050are indicated. Each photograph is illuminated with different input illumination that extends from the visible through the NIR portion of the spectrum. The entire spectrum of illumination for each measurement is shown in the photographs1030,1050. The illumination for the entire measured spectrum shares the same imaging dispersive element and all spectral components separated by the dispersive element fall onto the same modulator element. A clear spatial gap is apparent between the illuminated regions1032,1034in the first photograph1030and also between the illuminated regions1052,1054in the second photograph1050. This is necessary to provide independent spectral control for the NIR regions1032,1052and the visible regions1034,1054. For modulators that are pixelated modulators with a two dimensional array of pixels, it is clear that the pixels for the NIR region1032,1052are different from the pixels for the visible region1034,1054. It is also clear that individual spectral components of the visible and/or the NIR regions are distinct, and also can be independently controlled by controlling different regions of pixels on the pixelated modulator.

FIG. 11Aillustrates a graph1100of spectra from an embodiment of the spectral shaper system of the present teaching with rows of mirrors configured in the “on state” showing a comparison of the visible spectrum and the NIR spectrum. The spectral shaper system used for these measurements included a DMD with micro-mirrors as pixels at the modulator plane. These measurements were taken at the output of a liquid light guide that was optically coupled to the output of the spectral shaper system. For this measurement, eight rows of mirrors, with each row having a five-mirror width, was turned on. The visible spectrum1102is shown in short dashed line and the NIR spectrum1104is shown in a longer dash line. The combined spectrum1106is also shown with a solid line. The eight peaks apparent in the visible spectrum1102have a small full width at half maximum (FWHM). Five of the eight peaks of the NIR spectrum1104have lower counts and slightly broader FWHM. Some imbalance of the intensity of the spectra in the graph1100are due to attenuation in the liquid light guide, which has low transmission for wavelengths greater than 730 nm that collected the output light.

FIG. 11Billustrates a graph1150of spectra from the spectral shaper system described in connection with ofFIG. 11Ashowing the output with all the mirrors in the “on state” for the visible spectrum and/or the NIR spectrum. The visible spectrum1152with all mirrors in the “on state” in the visible region of the modulator is shown in short dashed line and the NIR spectrum1154with all mirrors in the “on state” in the NIR region is shown in a longer dash line. The combined spectrum1156with all mirrors in the “on state” in both regions is also shown with a solid line. With all mirrors in the “on state”, the output exhibits a higher count rate with individual spectral components not distinguished, and the total wavelength range is lower than the rows in on state of graph1100.

FIG. 12Aillustrates a graph1200of a spectrum from an embodiment of the spectral shaper system of the present teaching with rows of mirrors in the “on state” in the visible region. This graph shows results with eight rows of five mirror with each mirror in the “on state”. The high resolution provided by the aberration-corrected imaging is illustrated by the small FWHM.

FIG. 12Billustrates a graph1230of a spectrum from an embodiment of the spectral shaper of the present teaching with rows of mirrors in the NIR region in the on state. The NIR peaks have a wider FWHM.

FIG. 12Cillustrates a graph1250of both the visible spectrum and the NIR spectrum ofFIGS. 12A and 12Bon the same plot. The comparison shows lower throughput for the NIR light, and the larger FWHM. The liquid light guide used for this measurement had low transmission for the NIR region, but extended transmission liquid light guides are available with over 70% transmission throughout the near infrared region. Throughput of the spectral shaping system can be improved by extending the reflectivity of the imaging dispersive device by using, for example, a gold coated reflective surface that can result in as much as 10% higher flux. Also, changes in the aberration condition can modify the tilt of the individual lines in the NIR spectrum.

FIG. 13Aillustrates a graph1300of a spectrum from an embodiment of the spectral shaper system of the present teaching with five peaks in the NIR region using five rows of mirrors in the “on state” in the NIR region. The sample peaks are at 716 nm, 754 nm, 791 nm, 835 nm and 905 nm.

FIG. 13Billustrates a graph1350of the spectrum ofFIG. 13Bwith calculated FWHM information. The peak at 716 nm has a FWHM of 13.72 nm. The peak at 754 nm has a FWHM of 14.26 nm. The peak at 791 nm has a FWHM of 14.46 nm. The peak at 835 nm has a FWMH of 14.22 nm. The peak at 905 nm has a FWHM of 13.21 nm. Thus, the FWHM ranges from 13 nm to 14 nm.

One feature of the present teaching is that it is possible to have both the NIR optical source light and the visible source light be generated by the same optical source. The optical source is constructed so that the visible source light is provided at a plane consistent with the visible input plane of the spectral shaper and the NIR source light is provided at a plane consistent with the NIR input plane of the spectral shaper as described herein. One advantage of this embodiment is that both complexity and cost are reduced by using a single source to power both the visible and NIR illumination. This design makes it possible to provide a compact NIR-extended programmable light source using the spectral shaping system.

FIG. 14Aillustrates a front view1400of an optical source that generates visible light1402and NIR optical light1404from a broadband point source1406of light. The broadband point source1406of light can be, for example, generated by a high-intensity plasma of a laser driven light source. A first elliptical mirror1408reflects and focuses light from the point source1406to a visible output1410optical beam with a desired shape at a visible output plane1412. A short pass filter1414is positioned in the path of the light reflected from the first elliptical mirror1408. A second elliptical mirror1416reflects and focuses light from the point source1406to a NIR output1418optical beam with a desired shape at a NIR output plane1420. A long pass filter1422is positioned in the path of the light reflected from the second elliptical mirror1416. The shape of the visible output1410and the shape of the NIR output1418is elliptical, which, when coupled into the spectral shaper, serves to balance and smooth the spectrum of the visible and NIR parts of the spectrum at the shaper output.

FIG. 14Billustrates a top view1430of the optical source that generates visible light1402and NIR optical light1404ofFIG. 14A. The first and second elliptical mirrors1408,1416, short-pass filter1414and long pass filter1422are shown as well as the visible output plane1412and the NIR output plane1420.

FIG. 14Cillustrates a side top view1450of the optical source that generates visible light1402and NIR optical light1404(FIG. 14A). The first and second elliptical mirrors1408,1416, short-pass filter1414and long pass filter1422are shown as well as the visible output plane1412and the NIR output plane1420.

In various embodiments, the relative flux from the visible and NIR optical illumination can be achieved based on the reflectivity of various components used in the source. For example, it is possible to have nominally the same flux level for each channel of visible and/or NIR light. It is also possible to have higher flux in either the visible or the NIR regions. For example, using gold coating on reflective surfaces increases reflected flux of the infrared light. For example, a long-pass filter can flatten the Xenon spectrum response, reducing the peaks of Xenon spectrum in the near infrared. These two aspects can help improve the balance of the NIR part of the spectrum, especially as compared to the visible part of the spectrum of the output light of the optical source. For the visible light path, some embodiments use a first elliptical mirror1408with an enhanced aluminum coating and a short pass filter1414with a cutoff at 760 nm. For the NIR light path, some embodiments use a second elliptical mirror1416with an enhanced gold coating and a long-pass filter1422with a cutoff at 740 nm wavelength.

FIG. 15illustrates a graph1500of spectra of the output for different embodiments of the optical source for a spectral shaper system of the present teaching that use different filters and/or mirror coatings on the optical elements and a Xenon-based high-brightness plasma to generate the point source illumination. The first spectrum1502illustrates the output of the Xenon plasma, with high peaks in the near infrared region. The second spectrum1504illustrates the reduction of the NIR peaks using a long pass Xenon spectrum flattening filter with a cutoff wavelength of 740 nm.

FIG. 16illustrates an alignment and characterization system1600for an optical source1602for the spectral shaper system of the present teaching. An optical point source1612generates visible light1604at a visible output plane1606and NIR optical light1608at a NIR output plane1610from the optical point source1612. The optical point source1612for this embodiment is a high-intensity Xenon plasma driven by a laser. The visible light1604at a visible output plane1606and NIR optical light1608at a NIR output plane1610have nominally elliptical shapes. The visible light1604or the NIR light1608is coupled into an alignment tool1614that includes an imaging fiber bundle1616and a one-times magnifying lens pair1618that images the bundle onto a camera1620. A position of either the visible beam or the NIR beam on the camera is used to adjust the respective elliptical mirrors. As an example, if the optical point source1612has a plasma size of between 80 to 240 micrometers, it is imaged by a three-factor ellipsoidal mirror to a size between 240 and 720 micrometers at the output planes1606,1608. The inset picture1622shows a point source generated by an optical fiber as imaged at the camera to show the operation of the alignment tool1614in an ideal case.

EQUIVALENTS

While the Applicant's teaching is described in conjunction with various embodiments, it is not intended that the Applicant's teaching be limited to such embodiments. On the contrary, the Applicant's teaching encompasses various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art, which may be made therein without departing from the spirit and scope of the teaching.