Patent Description:
Various spectrographs are available in the marketplace. Known spectrographs generally require sophisticated active alignment. For example, a known spectrograph includes a slit that requires orientation under a microscope, and a diffraction element that requires mounting on an adjustable mount for alignment with the optical path of the spectrograph.

<CIT> discloses a handheld spectrometer with spectrograph having a beam inlet device, a dispersive element and a detector, wherein the spectrometer comprises adjustment means, so that the beam inlet device, the dispersive element and detector can be easily adjusted and aligned from the outside of the spectrograph housing.

<CIT> discloses a diffractive optical element including a diffraction grating and a flange, wherein the flange part comprises protrusions projecting outward from the outer circumferential face, which are used to position the diffractive optical element in a holder section formed in an optical pickup incorporated e.g. in a CD/DVD reproducing apparatus. The diffractive optical element is secured in the holder section with a coned spring disc.

<CIT> discloses a fiber optic coupler for use with a diode array spectrophotometer system that optimizes the optical interface between a first fiber optic waveguide employed to couple light from a sample under analysis and a diode array spectrograph. <CIT> discloses a coupler for coupling a linear fiber array to a spectrometer. <CIT> discloses a fast response etalon based spectrometer for spectral measurement of a pulse laser beam. A portion of the beam is directed through a double pass etalon device which provides angular separation of spectral components of the beam. <CIT> discloses a spectrum measuring instrument including a housing having a black inner surface, a concave diffraction grating provided in the housing, and a CCD detector. <CIT>discloses a monolithic Offner spectrometer with various components like a diffraction grating and a slit being manufactured by using a diamond machining process. The <CIT> discloses a spectroscopic characteristics acquisition unit with a lens array and a pinhole array whereby each of the lenses corresponds to one of the openings.

Exemplary embodiments of spectrographs described herein provide increased light energy in a desired spectral range or desired spectral ranges, and improved trapping of stray light, resulting in reduced or minimized stray light. In addition, exemplary spectrographs described herein are less susceptible to requiring redundant alignment. In addition, exemplary spectrographs described herein show an enhanced overall performance.

A spectrograph is disclosed which includes: a housing that includes a wall having an inner surface facing an interior of the housing, the wall including first, second and third openings, the wall including projections extending inwardly of the second opening; an entrance slit located at the first opening and configured to direct light along a first portion of a light path in the interior of the housing; a dispersive element located at the second opening and configured to receive light from the entrance slit along the first portion of the light path and direct light along a second portion of the light path in the interior of the housing, the dispersive element having a contour dimensioned to contact the projections which extend into the second opening, the second opening being constructed based on the dimensions and tolerances used to manufacture the dispersive element, the projections and the contour of the dispersive element having complementary dimensional parameters and complementary tolerance parameters so that the contour of the dispersive element contacts all of the projections when the dispersive element is at least partially located in the second opening, and so that an orientation of the dispersive element relative to the entrance slit is fixed; and a detector located at the third opening and configured to receive light from the dispersive element along the second portion of the light path.

The second opening includes inner and outer openings wherein the inner opening is located closer than the outer opening to the interior of the housing.

Furthermore, the projections include a first group of projections extending inwardly of the inner opening and a second group of projections extending inwardly of the outer opening.

At least one of the first group of projections or the second group of projections includes at least three projections.

In a further embodiment the inner opening and the outer opening can possess different diameters.

In another embodiment of the spectrograph, the detector includes a first group of light-sensitive regions and a second group of light-sensitive regions; and a cover being positioned to separate the first group of light-sensitive regions from the light path, the second group of light-sensitive regions being exposed to the light path.

The detector is preferably one of a charge-coupled device array detector, a linear charge-coupled device detector, a photo-diode array detector, or a complementary metal-oxide semiconductor detector.

In an embodiment the light-sensitive regions of the first group detect light in a first wavelength range and the light-sensitive regions of the second group detect light in a second wavelength range wherein the first and second wavelength ranges are different. In a variation of the aforementioned, the light-sensitive regions of the first group and the light-sensitive regions of the second group can detect light in a first and second non-overlapping wavelength range respectively.

In another embodiment, the spectrograph comprises a filter that is arranged in front of the detector such that light traveling along the second portion of the light path will first traverse the filter and then reach the detector.

In one embodiment of the spectrograph, the cover is integral with the wall of the housing. In another embodiment, the cover can be distinct from the wall of the housing.

In another embodiment of the spectrograph, the entrance slit including a wedged portion extending along a plane that is angled relative to the inner surface of the housing at the first opening; a dispersive element located at the second opening and configured to receive light from the entrance slit along the first portion of the light path and direct light along a second portion of the light path in the interior of the housing; and a detector located at the third opening and configured to receive light from the dispersive element along the second portion of the light path, the wedged portion being configured to fix the entrance slit at an orientation about the first portion of the light path and relative to the dispersive element.

In an embodiment the entrance slit includes a longitudinal gap extending at an angle of <NUM> degrees to the wedged portion.

In another embodiment an optical fiber can be provided in combination with the aforementioned spectrograph that is configured such that light is directed into the spectrograph through the optical fiber that is in optical communication with the entrance slit.

The spectrograph can further comprise a screw positioned against the wedged portion of the entrance slit to fix the entrance slit at a predetermined orientation. The entrance slit includes a flange at a periphery of the entrance slit wherein the wedged portion is a wedged portion of the flange.

In a further embodiment the spectrograph can be provided with an optical fiber that is configured such that light is directed into the spectrograph through the optical fiber wherein further the flange includes a tubular member housing the optical fiber in optical communication with the entrance slit.

Furthermore, a spectrometer comprising the aforementioned spectrograph and its aforementioned embodiments is disclosed and the spectrometer preferably comprises a light source, a measurement area configured to hold a sample or sample carrier, first optical elements configured to direct light from the light source to the measurement area, second optical elements configured to direct light from the measurement area to the entrance slit of the spectrograph.

Other features and advantages disclosed herein will become more apparent from the following detailed description of exemplary embodiments when read in conjunction with the attached drawings, wherein:.

<FIG>, <FIG> and <FIG> show exemplary embodiments of a spectrograph <NUM>. The spectrograph <NUM> includes a housing <NUM> that includes a wall <NUM> having an inner surface facing an interior of the housing <NUM>. The wall includes a first opening <NUM>, a second opening <NUM> and a third opening <NUM>. The spectrograph <NUM> includes an entrance slit <NUM> located at the first opening <NUM> and configured to direct light along a first portion LP1 of a light path in the interior of the housing <NUM>. The spectrograph <NUM> includes a dispersive element <NUM> located at the second opening <NUM> and configured to receive light from the entrance slit <NUM> along the first portion LP1 of the light path and direct light along a second portion LP2 of the light path in the interior of the housing <NUM>. The spectrograph <NUM> includes a detector <NUM> located at the third opening <NUM> and configured to receive light from the dispersive element <NUM> along the second portion LP2 of the light path.

In an exemplary embodiment of the spectrograph <NUM>, the housing <NUM> includes a black, anodized material, and/or any other material known in the art or to be developed to block light of a particular spectral range. In an exemplary embodiment, the first and third openings <NUM>, <NUM> are on the same side of the housing <NUM>, and the second opening <NUM> is on the opposite side of the housing <NUM>, such that light enters from one side of the housing <NUM> through the entrance slit <NUM>, is dispersed by the dispersive element <NUM> on the opposite side of the housing <NUM>, and reaches the detector <NUM> on the side of the housing <NUM> on which the entrance slit <NUM> is located. As shown in <FIG>, a housing cover <NUM> is arranged to close the housing <NUM> and provides a dark environment in the interior of the housing <NUM>.

In an exemplary embodiment of the spectrograph <NUM>, the light directed along the first portion LP1 of the light path by the entrance slit <NUM> comes from a fiber <NUM> in optical communication with the entrance slit <NUM>.

In an exemplary embodiment of the spectrograph <NUM>, the dispersive element <NUM> includes a transmission grating, a grooved grating, a holographic grating and/or a prism, and/or another suitable dispersive element known in the art or to be developed. In an exemplary embodiment, the dispersive element <NUM> includes a square plate, and an active area that is a concave circular reflective and diffractive surface.

In an exemplary embodiment, the spectrograph <NUM>, a light source and/or any or all optical components between the light source and the detector <NUM> are configured to operate in the "UV/Vis" (ultraviolet-visible) range. In other exemplary embodiments, the spectrograph <NUM>, a light source and/or any or all optical components between the light source and the detector <NUM> are configured to operate in either one, or in any combination of the following spectral ranges: UV/Vis, Vis (visible), MIR (mid infrared) and/or NIR (near infrared). For example, the detector <NUM> and/or the dispersive element <NUM> can be optimized for any or any combination of these ranges of the electromagnetic spectrum.

In an exemplary embodiment of the spectrograph <NUM>, the entrance slit <NUM> can be z-aligned, for focus alignment, by adjusting the distance traveled by light from the entrance slit <NUM> to the detector <NUM> via the dispersive element <NUM>. The detector <NUM> can be x/y-aligned, for focal plane alignment, by displacing the detector <NUM> in the plane of the detector <NUM>. The detector <NUM> can also be finely aligned manually using screws. The focal alignment on the entrance slit <NUM> can also be adjusted. The focus of the light can be optimized, to sharpen the light at the detector <NUM>.

In exemplary embodiments described herein, the performance of the spectrograph <NUM> can be enhanced by reducing or minimizing stray light, by increasing light energy in a desired spectral range or desired spectral ranges, and by adequately trapping stray light. In addition, exemplary embodiments described herein are less susceptible to requiring redundant alignment.

As shown in <FIG> and <FIG>, the detector <NUM> includes a first group of light-sensitive regions <NUM> and a second group of light-sensitive regions <NUM>. The spectrograph <NUM> includes a cover <NUM> positioned to separate the first group of light-sensitive regions <NUM> from the light path, the second group of light-sensitive regions <NUM> being exposed to the light path.

In an exemplary embodiment of the spectrograph <NUM>, the cover <NUM> blocks a zero-order signal of the light directed along the light path. In exemplary embodiments, this is desirable because, for example, the first-order signal is of interest for a spectroscopic measurement. Because the cover <NUM> blocks the zero-order signal, no separate light trap is needed, the light can remain focused on the detector <NUM>, and the zero-order light need not be directed toward a light trap and therefore away from the detector <NUM>. Stray light reaching the detector <NUM> is substantially reduced, and the risk of light leaking through pixel overflowing or scattered light is reduced or eliminated. Use of the cover <NUM> enables the measurement of dark current to obtain a compensation intensity value, and enables a simultaneous dark current measurement at the same temperature as a sample measurement. This can be desirable because measured light intensity is temperate-sensitive.

In an exemplary embodiment of the spectrograph <NUM>, the cover <NUM> is oriented so that the zero-order signal is absorbed by the cover <NUM> so that reduced or no light is reflected back to the dispersive element <NUM> and/or the entrance slit <NUM>, thus reducing stray light. The detector <NUM> can be tilted to match a curved focal plane of the light reflected by the dispersive element <NUM>.

In an exemplary embodiment of the spectrograph <NUM>, the detector <NUM> is one of a charge-coupled device (CCD) array detector, a linear CCD detector, a photo-diode array detector, or a complementary metal-oxide semiconductor (CMOS) detector, and/or another suitable detector known in the art or to be developed.

In an exemplary embodiment of the spectrograph <NUM>, the light-sensitive regions <NUM> of the first group detect light in a first wavelength range, the light-sensitive regions <NUM> of the second group detect light in a second wavelength range, and the first and second wavelength ranges are different.

In an exemplary embodiment of the spectrograph <NUM>, the light-sensitive regions <NUM> of the first group detect light in a first wavelength range, the light-sensitive regions <NUM> of the second group detect light in a second wavelength range, and the first and second wavelength ranges are non-overlapping.

In an exemplary embodiment, the spectrograph <NUM> includes a filter <NUM> arranged in front of the detector <NUM> such that light traveling along the second portion LP2 of the light path will first traverse the filter <NUM> and then reach the detector <NUM>. The light-sensitive regions <NUM> of the second group are exposed to the light path even if the filter <NUM> is disposed between the light-sensitive regions <NUM> of the second group and the interior of the housing <NUM>. In an exemplary embodiment, the filter <NUM> includes any filter known in the art or to be developed that suppresses higher order light from the dispersion element <NUM>. In an exemplary embodiment, the filter <NUM> is an order sorting filter. In an exemplary embodiment, the filter <NUM> contacts the detector <NUM>. In an exemplary embodiment, the filter <NUM> replaces the detector window used in known systems. In other words, the filter <NUM> is configured to perform the functions of an order sorting filter and a detector window. For example, the filter <NUM> reduces the likelihood of second or third-order light reaching the detector <NUM>.

In an exemplary embodiment of the spectrograph <NUM>, the cover <NUM> includes a black, anodized metal plate. Alternatively, the cover <NUM> can include any other material known in the art or to be developed to block light of a particular spectral range.

In an exemplary embodiment of the spectrograph <NUM>, the cover <NUM> is integral with the wall <NUM> of the housing <NUM>. For example, the cover <NUM> is continuous with and made from the same material as an adjacent portion of the wall <NUM> of the housing <NUM>.

In an exemplary embodiment of the spectrograph <NUM>, the cover <NUM> is distinct from the wall <NUM> of the housing <NUM>. In exemplary embodiments, the cover <NUM> is coupled to the wall <NUM> of the housing <NUM>. In other exemplary embodiments, the cover <NUM> is spaced from the wall <NUM> of the housing <NUM>.

As shown in <FIG> and <FIG>, the wall <NUM> includes projections <NUM> extending inwardly of the second opening <NUM>. The dispersive element <NUM> has a contour <NUM> dimensioned to contact the projections <NUM> which extend into the second opening <NUM>. The projections <NUM> and the contour <NUM> of the dispersive element <NUM> have complementary dimensional parameters and complementary tolerance parameters so that the contour <NUM> of the dispersive element <NUM> contacts all of the projections <NUM> when the dispersive element <NUM> is at least partially located in the second opening <NUM>, and so that an orientation of the dispersive element <NUM> relative to the entrance slit <NUM> is fixed. In an exemplary embodiment of the spectrograph <NUM>, the contour <NUM> of the dispersive element <NUM> contacts all of the projections <NUM> when a force is exerted on the dispersive element <NUM> in a direction toward the interior of the housing <NUM>.

Complementary dimensional parameters and complementary tolerance parameters are determined during manufacture such that the contour <NUM> of the dispersive element <NUM> is configured to contact all of the projections <NUM> when the dispersive element <NUM> is at least partially located in the second opening <NUM>, and so that the orientation of the dispersive element <NUM> is fixed. In other words, to account for the fact that dispersive elements <NUM> can be uniquely designed for specific applications, the second opening <NUM> is constructed based on the dimensions and tolerances used to construct the dispersive element <NUM> to be placed in the second opening <NUM>. As a result, shifts occurring during manufacture of the dispersive element <NUM> are taken into account when forming the second opening <NUM> and its projections <NUM>. The configuration of the projections <NUM> reduces the likelihood of additional alignment being necessary during assembly. In an exemplary embodiment, when a dispersive element <NUM> is manufactured, the dispersive element <NUM> is adjusted based on imperfections in the substrate of the dispersive element <NUM>. For example, the dimensions and the centering of the dispersive element <NUM> are adjusted. In an exemplary embodiment, the second opening <NUM> of the housing <NUM> is constructed based on these adjustments.

In the case of the spectrograph <NUM>, the second opening <NUM> includes inner and outer openings <NUM>, <NUM>. The inner opening <NUM> is located closer than the outer opening <NUM> to the interior of the housing <NUM>. The projections <NUM> include a first group of projections 122A extending inwardly of the inner opening <NUM> and a second group of projections 122B extending inwardly of the outer opening <NUM>.

In the case of the spectrograph <NUM>, at least one of the first group of projections 122A or the second group of projections 122B includes at least three projections <NUM>. In exemplary embodiments of the spectrograph <NUM>, the first 122A and/or second group 122B of projections can include two projections, or more than three projections. In exemplary embodiments, the projections <NUM> are configured to reduce the risk of the dispersive element <NUM> tilting in any direction relative to the second opening <NUM>. In an exemplary embodiment, the projections 122A of the first group are contact spots that include three hemispherical nudges protruding toward the reflective and/or diffractive surface of the dispersive element <NUM> such that the this surface faces the detector <NUM> and the slit <NUM> when positioned in the inner opening <NUM>.

In an exemplary embodiment of the spectrograph <NUM>, the inner opening <NUM> and the outer opening <NUM> possess different diameters. In an exemplary embodiment, the inner opening <NUM> and the outer opening <NUM> possess different shapes.

As shown in <FIG>, the entrance slit <NUM> includes a wedged portion <NUM> extending along a plane that is angled (i.e., inclined by a non-zero angle) relative to the inner surface of the housing <NUM> at the first opening <NUM>. The wedged portion <NUM> is configured to fix the entrance slit <NUM> at an orientation about the first portion LP1 of the light path and relative to the dispersive element <NUM>.

In an exemplary embodiment of the spectrograph <NUM>, the entrance slit <NUM> includes a longitudinal gap <NUM> extending at an angle of <NUM> degrees to the wedged portion <NUM>, as illustrated in <FIG>, which shows an exemplary entrance slit <NUM> In other exemplary embodiments, the longitudinal gap <NUM> extends at any other angle relative to the wedged portion <NUM>.

An exemplary embodiment, the spectrograph <NUM> is combined with an optical fiber <NUM> that is configured such that light is directed into the spectrograph <NUM> through the optical fiber <NUM>. The optical fiber <NUM> is in optical communication with the entrance slit <NUM>.

An exemplary embodiment of the spectrograph <NUM> includes a screw <NUM> positioned against the wedged portion <NUM> of the entrance slit <NUM> to fix the entrance slit <NUM> at a predetermined orientation. The configuration of the entrance slit <NUM> and its wedged portion <NUM> reduces the likelihood of additional alignment being necessary during assembly, unlike known entrance slits which are aligned under a microscope.

In an exemplary embodiment of the spectrograph <NUM>, the entrance slit <NUM> includes a flange <NUM> at a periphery of the entrance slit <NUM>, the wedged portion <NUM> being a wedged portion of the flange <NUM>.

In an exemplary embodiment, the spectrograph <NUM> is combined with an optical fiber <NUM> that is configured such that light is directed into the spectrograph <NUM> through the optical fiber <NUM>. The flange <NUM> includes a tubular member housing the optical fiber <NUM> in optical communication with the entrance slit <NUM>. In an exemplary embodiment, the tubular member is a ferrule.

<FIG> shows an exemplary embodiment of an entrance slit <NUM>. A flange <NUM> of the slit <NUM> houses two fibers <NUM>. The fibers <NUM> are adjacent to one another and are aligned in a direction perpendicular to the wedged portion <NUM>. In other exemplary embodiments, the longitudinal gap <NUM> extends at any other angle relative to the wedged portion <NUM>.

<FIG> shows an exemplary embodiment of a spectrometer <NUM>, which includes a spectrograph <NUM>, a light source <NUM>; a measurement area <NUM> configured to hold a sample or sample carrier; first optical elements <NUM> configured to direct light from the light source <NUM> to the measurement area <NUM>; second optical elements <NUM> configured to direct light from the measurement area <NUM> to the entrance slit <NUM>. The first optical elements <NUM> include a first optical fiber, such as a glass fiber <NUM>.

In exemplary embodiments, the first optical elements <NUM> are configured such that light in a portion of the light path between the light source <NUM> and the second optical elements <NUM> is directed so as to propagate through a sample without being blocked by other components of the spectrometer and so as to be collected by the optical fiber <NUM>. In an exemplary embodiment, the light is focused on or within the sample. In an exemplary embodiment, the light is substantially collimated between the first and second optical elements. In an exemplary embodiment, the optical characteristics of the glass fiber <NUM>, optionally in combination with a collimator lens <NUM> (and/or a collimator mirror) at the end of the glass fiber <NUM>, ensure that the beam is directed so as to propagate through a sample without being blocked by other components of the spectrometer and so as to be collected by the optical fiber <NUM>, focused on or within the sample, or substantially collimated between the first and second optical elements. A spectrometer constructed with glass fibers can be built more compact than known benchtop spectrometers.

The second optical elements <NUM> include a second optical fiber such as a glass fiber <NUM>. In exemplary embodiments the first and second optical elements <NUM> and <NUM> include optical elements such as lenses and mirrors to transmit the light along the light path from the light source <NUM> to the detector <NUM>. In an exemplary embodiment, a lens focuses collimated light onto the glass fiber <NUM>. In exemplary embodiments, all optical elements in the light path, including for example the light source <NUM>, the first and second optical elements <NUM> and <NUM>, the glass fibers <NUM> and <NUM>, the filter <NUM> (not shown in <FIG>), and the detector <NUM>, are optimized for a particular spectral range. In an exemplary embodiment, the detector <NUM> is disposed on a sensor chip <NUM> that includes a processor and non-transitory computer-readable memory and that is connected to a display <NUM> or via a computer for further processing to a display <NUM>.

It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims.

Claim 1:
A spectrograph (<NUM>) comprising:
a housing (<NUM>) that includes a wall (<NUM>) having an inner surface facing an interior of the housing, the wall including first (<NUM>), second (<NUM>) and third openings (<NUM>), the wall including projections (<NUM>) extending inwardly of the second opening (<NUM>);
an entrance slit (<NUM>) located at the first opening (<NUM>) and configured to direct light along a first portion of a light path (LP1) in the interior of the housing (<NUM>);
a dispersive element (<NUM>) located at the second opening (<NUM>) and configured to receive light from the entrance slit (<NUM>) along the first portion of the light path (LP1) and direct light along a second portion of the light path (LP2) in the interior of the housing (<NUM>); and
a detector (<NUM>) located at the third opening (<NUM>) and configured to receive light from the dispersive element (<NUM>) along the second portion of the light path (LP2);
characterized in that the dispersive element (<NUM>) has a contour (<NUM>) dimensioned to contact the projections (<NUM>) which extend into the second opening (<NUM>), the projections (<NUM>) and the contour (<NUM>) of the dispersive element (<NUM>) having complementary dimensional parameters and complementary tolerance parameters so that the contour (<NUM>) of the dispersive element (<NUM>) contacts all of the projections (<NUM>) when the dispersive element (<NUM>) is at least partially located in the second opening (<NUM>), and so that an orientation of the dispersive element (<NUM>) relative to the entrance slit (<NUM>) is fixed wherein the second opening (<NUM>) includes inner (<NUM>) and outer openings (<NUM>), the inner opening (<NUM>) being located closer than the outer opening (<NUM>) to the interior of the housing, the projections (<NUM>) including a first group of projections (122A) extending inwardly of the inner opening and a second group of projections (122B) extending inwardly of the outer opening., wherein at least one of the first group of projections (122A) or the second group of projections (122B) includes at least three projections.