Patent Description:
Aspects of this invention relates generally to a device that provides a variable sized aperture for analyzing a sample with infrared spectroscopy.

Fourier transform infrared (FTIR) spectrometry was developed to overcome limitations of dispersive spectrometry techniques, particularly the slow scanning process. With FTIR, all infrared (IR) frequencies can be measured simultaneously, rather than individually, with a simple optical device referred to as an interferometer. An interferometer produces a unique signal containing all IR frequencies "encoded" within it. This signal can be measured very quickly, e.g., within approximately one second, thereby reducing the time element per sample to a matter of only a few seconds rather than several minutes.

Most interferometers employ a beamsplitter which receives an incoming IR beam and divides it into two optical beams. One beam is reflected by a flat mirror which is fixed in place. The other beam is reflected by a movable flat mirror which is controlled to move back and forth over a short distance (e.g., a few millimeters). The resulting two reflected beams are recombined when they meet back at the beamsplitter.

When only a portion of a sample is to be analyzed, an aperture may be used to control the size and shape of the infrared beam. A variable aperture can be used so as to be able to vary the aperture size and shape to correspond to the size and shape of the sample area to be observed. Some devices use a variable aperture device that includes four jaws controlled by motors and gears that work together to provide an aperture of varying size and shape.

It would be desirable to provide a device that provides a variable sized aperture that reduces or overcomes some or all of the difficulties inherent in prior known processes. Particular objects and advantages will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of certain embodiments. <CIT> discloses a flexible optical aperture mechanism. <CIT> discloses a scanning apparatus for biological microdenisitometry. <CIT> a lens system for photographing stereoscopic images. <CIT> discloses a method and apparatus for dense spectrum unmixing and image reconstruction of a sample.

In accordance with an example useful for understanding the disclosure, an apparatus for providing a variable sized aperture for an imaging device includes a first plate having a first plurality of plate apertures extending therethrough and a second plate having a second plurality of plate apertures extending therethrough. A first motor is operably connected to the first plate and a second motor is operably connected to the second plate. The first and second motors are configured to move the first plate and the second plate with respect to one another so as to align any of the first plurality of plate apertures with any of the second plurality of plate apertures to define a plurality of light beam apertures.

In accordance with a first aspect, an imaging device according to claim <NUM> is provided.

In accordance with other aspects, the imaging device may include a controller connected to the first and second motors and the detector. The imaging device may also include a beam splitter and a monitor to allow a user to view an area of the sample to be analyzed.

These and additional features and advantages disclosed here will be further understood from the following detailed disclosure of certain embodiments.

The figures referred to above are not drawn necessarily to scale, should be understood to provide a representation of particular embodiments of the invention, and are merely conceptual in nature and illustrative of the principles involved. Some features of the imaging device depicted in the drawings have been enlarged or distorted relative to others to facilitate explanation and understanding. The same reference numbers are used in the drawings for similar or identical components and features shown in various alternative embodiments. Imaging devices as disclosed herein would have configurations and components determined, in part, by the intended application and environment in which they are used.

<FIG> illustrates as a representative imaging device a common FTIR spectrometer <NUM> that includes an IR source <NUM>, a collimator <NUM> and an interferometer <NUM> (e.g., a Michelson interferometer). The interferometer <NUM> includes a beamsplitter <NUM>, a fixed mirror <NUM> and a movable mirror <NUM>. The source <NUM> generates IR radiation <NUM> which the collimator <NUM> aligns to produce parallel rays of light <NUM>. The collimated IR signal <NUM> is encoded with an interferogram <NUM> by interferometer <NUM>, passes through a first focus element <NUM>, and then irradiates a sample <NUM> typically housed in a sample compartment 13A.

The resulting IR signal <NUM> containing energy not absorbed by the sample is passed through a second focus element <NUM> and a third focus element <NUM> and then is detected by a detector <NUM>. The focus elements may be magnifying lenses or mirrors when longer infrared wavelengths of light are used.

The IR signal is then amplified and converted to a digital signal by an amplifier and analog-to-digital converter (ADC), respectively (not shown), for processing by a controller <NUM>, in which a Fourier transform is computed. Though not shown here, also included is a laser source that provides a reference signal. As is known in the art, the zero amplitude crossings of this reference signal define the discrete time intervals during which the interferogram is sampled.

Typically only a portion of sample <NUM> is to be analyzed. In order to obtain a measurement of only a portion of the sample, it is desirable to limit the light reaching detector <NUM>. This eliminates light from other areas of the sample so that the light contains pure spectral information, which improves analysis of the sample.

In order to measure a portion of sample <NUM>, an aperture controlling assembly <NUM> is positioned between second focus element <NUM> and third focus element <NUM>, and may include a first motor <NUM> connected to a first plate <NUM> that includes a plurality of first plate apertures <NUM> (only one aperture <NUM> is visible in <FIG>). First motor <NUM> may be connected to first plate <NUM> by a first shaft <NUM>. A second motor <NUM> may be connected by way of a second shaft <NUM> to a second plate <NUM> that includes a plurality of second plate apertures <NUM> (only one aperture <NUM> is visible in <FIG>). First motor <NUM> and second motor <NUM> may be stepper motors or any other motor suitable to rotate first plate <NUM> and second plate <NUM>, respectively.

As described in greater detail below, first motor <NUM> and second motor <NUM> are activated by controller <NUM> to rotate first plate <NUM> and second plate <NUM>, respectively to align selected plate apertures of first plate <NUM> and second plate <NUM> to define a light beam aperture <NUM>, so that the beam that passes to detector <NUM> matches the size and shape of sample <NUM> to be analyzed.

As seen in <FIG>, first plate <NUM> may include a first plurality of plate apertures <NUM> and second plate <NUM> may include a second plurality of plate apertures <NUM>. In the illustrated embodiment, plate apertures <NUM> are rectangular apertures and plate apertures <NUM> are circular apertures.

As illustrated here, each of first plate <NUM> and second plate <NUM> is a circular disk. It is to be appreciated that first plate <NUM> and second plate <NUM> can have a shape other than circular. In certain embodiments, first plate <NUM> and second plate <NUM> are each formed of a thin plate of metal. Plate apertures <NUM> may be photo etched or laser cut into first plate <NUM>, for example. It is to be appreciated that first plate <NUM> and second plate <NUM> may be formed of any desired material.

A common sample to be examined is a thin film, where the thickness of the sample is small enough that a simple round aperture will work. However, small round apertures may provide a low amount of collected light, resulting in a weak and noisy spectra that must be collected over a long period of time to reduce the noise level to an acceptable level. By using a rectangular aperture, <NUM> to <NUM> times more light can be passed through, greatly speeding up the collection of data. As discussed below, first plate <NUM> and second plate <NUM> may include a combination of circular and rectangular apertures.

When first plate <NUM> and second plate <NUM> are overlapped such that a beam of light can pass through a first pair of plate apertures <NUM>, <NUM>, as illustrated <FIG> and <FIG>, the first pair of plate apertures forms a light beam aperture <NUM> having a width W defined by plate aperture <NUM> of first plate <NUM> and a height H defined by plate aperture <NUM> of second plate <NUM>. Thus the beam of light that passes through this pair of plate apertures takes on a shape defined by the plate aperture <NUM> of first plate <NUM> and the plate aperture <NUM> of second plate <NUM>. As seen here light beam aperture <NUM> is nearly rectangular in shape, with its sides extending substantially straight and its ends being slightly curved. In certain embodiments, light beam aperture <NUM> may have an aspect ratio of approximately <NUM>:<NUM> such that height H is approximately <NUM> times width W.

As used herein, the phrase "substantially" is intended to modify the term is it used with to mean mostly, or almost completely. For example, the phrase "substantially straight" is intended to mean straight, or almost completely straight, within the constraints of sensible, commercial engineering objectives, manufacturing tolerances, costs, and capabilities in the field of imaging systems.

First plate <NUM> and second plate <NUM> may be positioned closely to one another such that they essentially are at the same optical focus. In certain embodiments, the distance between first plate <NUM> and second plate <NUM> may be between approximately <NUM> (<NUM>") and approximately <NUM> (<NUM>"). In certain embodiments, first plate <NUM> and second plate <NUM> may even be in contact with one another.

In the embodiment illustrated in <FIG>, plate apertures <NUM> are positioned along a circle proximate a peripheral edge <NUM> of first plate <NUM>. It is to be appreciated that plate apertures <NUM> are shown here with rectangular shapes as an exemplary shape for use with imaging device <NUM>. It is to be appreciated that plate apertures <NUM> can have different shapes other than rectangular. Further, it is to be appreciated that the number and sizes of plate apertures <NUM> formed in first plate <NUM> can vary as well. In the example illustrated in <FIG>, plate <NUM> includes four groups of substantially rectangularly shaped apertures (e.g. subsets <NUM>, <NUM>, <NUM>, and <NUM>) that all have apertures of about the same length but each group having a different width from the other groups. In the present example, each group comprises <NUM> apertures although this should not be considered as limiting because of choice or due to the fact that embodiments of plate <NUM> may be larger or smaller which may increase or reduce the area available and thus may affect aperture number in each group. Similarly, plate <NUM> may include more or fewer groups for the same reasons.

More specifically as illustrated in the example of <FIG>, a first subset <NUM> of the plurality of plate apertures <NUM> is positioned in one quadrant of first plate <NUM>. Each of the plate apertures <NUM> in first subset <NUM> has the same size as the other plate apertures in first subset <NUM> and may extend substantially parallel to one another. It is to be appreciated that additional apertures may be provided between the apertures seen in first subset <NUM>, but are not shown here for purposes of clarity. As <FIG> illustrates, first subset <NUM> has half of the apertures removed to make it easier to understand with subset <NUM> having a plurality of rectangular apertures <NUM> that are substantially parallel to each other but each have a slightly different angular relationship relative to the circumference of first plate <NUM>. Therefore, if first plate <NUM> is rotated by some amount such as, for instance, <NUM> degrees, apertures <NUM> all rotate relative to a fixed location such as the field of view associated with the microscope optics. Thus, the angular relationship of the rectangular shape of a second embodiment of aperture <NUM> in the field of view includes a <NUM> degree rotational difference relative to the previous first embodiment of aperture <NUM> in the field of view. In other words, because the plate apertures <NUM> in first subset <NUM> are offset from one another along the circle on which they are positioned, each aperture <NUM> lines up with a corresponding aperture <NUM> in a different orientation than the other plate apertures <NUM> in subset <NUM> as the plates are rotated. This provides control of the angle of the rectangle of aperture <NUM> in the field of view that enables matching the shape of aperture <NUM> to the angle of a given sample to within plus or minus <NUM> degrees in a very cost effective way.

Additional apertures are seen in other quadrants of first plate <NUM> as discussed below. For example, the sizes of apertures <NUM> in subsets <NUM>, <NUM>, and <NUM> are shown with an additional set of apertures <NUM> that are substantially parallel to one another and positioned at a <NUM> degree rotation relative to the first set of substantially parallel apertures <NUM> which are in substantially the same positional relationship to first plate <NUM> as apertures <NUM> in first subset <NUM>. This allows a near doubling of the number of apertures <NUM> in subsets <NUM>, <NUM>, and <NUM> in the same space which also provides for more positional choices of apertures <NUM> in the field of view.

As noted above, the light beam aperture <NUM> is optimally aligned with the portion of the sample to be analyzed. If the rectangular shaped light beam aperture is not rotated to match the angle/orientation of the sample, light from unwanted nearby layers of the sample thin film will be collected, causing errors in the measured spectra. Therefore first plate <NUM> is provided with a variety of rectangular apertures that are selectable in small steps of rotation (about <NUM> degrees) to allow close matching of the orientation of the sample to the orientation of the light beam aperture <NUM>.

The different angled orientations of the apertures can be seen by comparing the light beam aperture <NUM> formed by plate apertures <NUM>, <NUM> seen in <FIG> with the light beam aperture <NUM> formed by plate apertures <NUM>, <NUM> seen in <FIG>. A longitudinal axis L of light beam aperture <NUM> in <FIG> has an angle α with respect to a radius R of first plate <NUM> and second plate <NUM>. A longitudinal axis L of light beam aperture <NUM> in <FIG> has an angle β with respect to radius R, with angle β being larger than angle α. Thus, it can be seen that the longitudinal axis L of each of the apertures <NUM> formed when plate apertures <NUM> in first subset <NUM> are overlapped with a particular aperture <NUM> of second plate <NUM> will have a different angle with respect to the radius R of the plates than each of the other apertures <NUM> so formed.

As seen in the embodiment illustrated in <FIG>, a second subset <NUM> has a plurality of plate apertures <NUM> positioned in a second quadrant of first plate <NUM>. Each of the plate apertures <NUM> in second subset <NUM> has the same size as the other plate apertures in second subset <NUM>, with that size being smaller than the size of the plate apertures of first subset <NUM>.

In second subset <NUM>, plate apertures <NUM> are positioned alternately substantially parallel and substantially rectangular to one another along the circle on which they are positioned. This provides for additional different orientations than those seen in first subset <NUM>, where plate apertures <NUM> are only disposed substantially parallel to one another and the perpendicularly oriented apertures <NUM> have been removed for clarity.

A third subset <NUM> has a plurality of plate apertures <NUM> positioned in a third quadrant of first plate <NUM>. Each of the plate apertures <NUM> in third subset <NUM> has the same size as the other plate apertures in third subset <NUM>, which is smaller than the plate apertures of first subset <NUM> and second subset <NUM>.

In a similar manner as that seen in second subset <NUM>, third subset <NUM> has plate apertures <NUM> that are positioned alternately substantially parallel and substantially rectangular to one another along the circle on which they are positioned.

A fourth subset <NUM> has a plurality of plate apertures <NUM> positioned in a fourth quadrant of first plate <NUM>. Each of the plate apertures <NUM> in fourth subset <NUM> has the same size as the other plate apertures in fourth subset <NUM>, which is smaller than the plate apertures of first subset <NUM>, second subset <NUM>, and third subset <NUM>.

In a similar manner as that seen in second subset <NUM> and third subset <NUM>, fourth subset <NUM> has plate apertures <NUM> that are positioned alternately substantially parallel and substantially rectangular to one another along the circle on which they are positioned.

As seen in <FIG>, second plate apertures <NUM> of second plate <NUM> are all circular and are positioned along a circle positioned proximate a peripheral edge <NUM> of second plate <NUM>. Each second aperture <NUM> has a diameter different than each of the other second plate apertures <NUM>. In the example of <FIG>, second plate <NUM> comprises <NUM> embodiments of aperture <NUM>, however it will be appreciated that second plate <NUM> may comprises different numbers of aperture <NUM> such as about <NUM>. Further, in the present example the diameters of apertures <NUM> may be smaller than the largest dimension of rectangular aperture <NUM> in first plate <NUM>, although one or more or of apertures <NUM> may be of substantially the same or larger dimension. Passing light through both plates <NUM> and <NUM> allows the diameter of the round holes to define <NUM> different lengths of the rectangular apertures <NUM>. Therefore any of apertures <NUM> can have about <NUM> different lengths with slightly rounded end as defined by the diameter of one of apertures <NUM> in plate <NUM>.

It should be noted that by the addition of one at least large aperture <NUM> with apertures <NUM> it is possible to have a set of substantially round shapes (e.g. <NUM> possibilities) of the light passing through plates <NUM> and <NUM> to choose from for samples that are substantially round. For example, the combination of <NUM> hole sizes and <NUM> different rectangle widths give <NUM> x <NUM> = <NUM> rectangle sizes to choose from and that each of the <NUM> rectangles can be rotated to <NUM> different angles give <NUM> x <NUM>= <NUM> different rectangular aperture + <NUM> round apertures for a total of <NUM> different apertures to allow a good match to a very wide range sample sizes and shapes.

As noted above, first plate apertures <NUM> and second plate apertures <NUM> are positioned along circles proximate the peripheral edges <NUM>, <NUM> of first plate <NUM> and second plate <NUM>, respectively, such that they can align with one another as the plates are rotated by first and second motors <NUM>, <NUM>. When a sample <NUM> to be studied is in position in imaging device <NUM>, first and second motors <NUM>, <NUM> are activated to rotate first plate <NUM> and/ or second plate <NUM> such that an aperture <NUM> of first plate <NUM> is overlapped with one of the plate apertures <NUM> of second plate <NUM>, thus defining a light beam aperture <NUM> that is sized to match the size of the sample to be studied.

By allowing each of first plate <NUM> and second plate <NUM> to be rotated, and by providing each of first plate <NUM> and second plate <NUM> with a variety of plate apertures of different shapes and sizes, a large number of apertures <NUM> can be defined, with each light beam aperture <NUM> being formed to have a different size and orientation than each of the other apertures <NUM> so formed. This provides for a large number of aperture sizes and shapes that can be used to match a light beam size and shape to the size and shape of the portion of the sample to be studied with imaging device <NUM>.

It is to be appreciated that the number of plate apertures provided in each of first plate <NUM> and second plate <NUM> can be varied. When more plate apertures are provided in a plate, the difference in the angle of orientation of the slots can be smaller. As fewer plate apertures are provided about the plate, the difference in the angle of orientation of the slots will increase.

An example useful for understanding the disclosure is illustrated in <FIG>. In this example, first plate apertures <NUM> of first plate <NUM> are all rectangular in shape, and are positioned along a circle positioned proximate peripheral edge <NUM> of first plate <NUM>. Each of first plate apertures <NUM> has a different size than the other first plate apertures <NUM>. In this example, second plate apertures <NUM> of second plate <NUM> are also all rectangular in shape, and are positioned along a circle proximate peripheral edge <NUM> of second plate <NUM>. As seen in <FIG>, when a first aperture <NUM> and a second aperture <NUM> of this embodiment overlap, the light beam aperture <NUM> so defined is also rectangular in shape and height H defined by aperture <NUM> of first plate <NUM> and a width W defined by an aperture <NUM> of second plate <NUM>. The number of rectangular sizes and widths possible in this embodiment are large, offering good size control over a wide range of sample sizes. However, the rotation of the rectangular light beam aperture <NUM> is fixed. It is to be appreciated that it is possible to add a third motor and a mechanical bearing and support system to rotate the entire aperture controlling assembly <NUM> around the selected light beam aperture <NUM> in order to align light beam aperture <NUM> with the sample. Also in examples where the rectangle shape aperture can be rotated by the third motor then only one aperture per size may be needed which provides some space savings.

As noted above, first plate <NUM> and second plate <NUM> may have shapes other than the circular shapes discussed and illustrated above. For example, as seen in <FIG>, first plate <NUM> and second plate <NUM> may be rectangular in shape. As illustrated here, first plate apertures <NUM> of first plate <NUM> are rectangular in shape and may vary in size and orientation. For example, there are different sized first plate apertures <NUM>. As seen here, second plate apertures <NUM> may be circular in shape and may similarly vary in dimension. Other shapes for first plate apertures <NUM> and second plate apertures <NUM> are also considered to be within the scope of this embodiment.

In such an embodiment, first motor <NUM> and second motor <NUM> would be configured to move first plate <NUM> laterally back and forth in a direction A and second plate <NUM> laterally back in forth in a direction B that, for example may extend substantially parallel to direction A. However, direction B may be at any angle relative to direction A that is desired and is not limited to a parallel direction.

Similar to the embodiments illustrated in <FIG>, in the embodiment of <FIG> each first aperture <NUM> may have a longitudinal axis L that is oriented at a different angle than the longitudinal axis L of the other first plate apertures <NUM> of first plate <NUM>. This provides for apertures <NUM> of different orientations when first plate <NUM> and second plate <NUM> are overlapped and first plate apertures <NUM> are aligned with a corresponding second aperture <NUM>.

Overall, aspects of the invention are directed to sample isolation devices, analytical instruments, and methods for sample analysis, which may be associated with greatly simplified sample preparation steps, compared to conventional steps. Those having skill in the art, with the knowledge gained from the present disclosure, will recognize that various changes can be made to the disclosed apparatuses and methods in attaining these and other advantages, without departing from the scope of the present invention. As such, it should be understood that the features described herein are susceptible to modification, alteration, changes, or substitution. The specific embodiments illustrated and described herein are for illustrative purposes only, and not limiting of the invention as set forth in the appended claims.

Another embodiment of a FTIR spectrometer <NUM> is seen in <FIG>, which shows how a user can optimize the shape and orientation, or alignment, of light beam aperture <NUM> with respect to sample <NUM>. In this embodiment, IR signal <NUM> is reflected by an IR dichroic beam splitter <NUM> through a reflective focus lens <NUM> into aperture controlling assembly <NUM> and then through another reflective focus lens <NUM> and onward to IR detector <NUM>.

A camera <NUM> and a focus lens <NUM> are positioned in line with IR signal <NUM> to allow the user to see a full view of the sample <NUM> in sample container 13A at all times. The user can advantageously employ camera <NUM> to optimize the size of the light beam aperture <NUM> provided by the aperture controlling assembly <NUM> as well as properly orient light beam aperture <NUM> with respect to sample <NUM>.

Light from a white Köhler sample illuminator <NUM> travels through a focus lens <NUM> and is reflected by a <NUM>/<NUM> white light beam splitter <NUM> to illuminate sample <NUM> in sample container 13A. Light from an aperture illuminator <NUM> (e.g., a bright red aperture illuminator) can be transmitted through a focus lens <NUM>, and then reflected off of a mirror <NUM> into and through aperture controlling assembly and onward to sample <NUM>. The light from aperture illuminator <NUM> is used to superimpose an image of sample aperture <NUM> onto sample <NUM> so that the user can ensure that the size and orientation of sample aperture <NUM> matches the area of sample <NUM> to be analyzed. By having aperture illuminator <NUM> project a different color light (red) on the sample, it allows the user to more clearly distinguish the illuminated border of sample aperture <NUM>.

The user then views the sample that is highlighted with the light from aperture illuminator <NUM>, and the user then employs controller <NUM> to activate first and second motors <NUM>, <NUM> and rotate first and second plates <NUM>, <NUM> to mate the size and orientation of sample aperture <NUM> with the area of sample <NUM> to be analyzed.

Since the light from aperture illuminator <NUM> is near IR detector <NUM> it will naturally block some of the light going to IR detector <NUM>. Thus, it is to be appreciated that once sample aperture <NUM> is properly sized and oriented, aperture illuminator <NUM> can be moved out of the light beam, allowing more light to reach IR detector <NUM> during data collection.

It is to be appreciated that reflective optics could be used in place of the transmission optics described in this embodiment. This can be advantageous in some embodiments since reflective optics and be used with longer wavelength IR light. Standard lenses have been used for illustration purposes to enhance clarity.

Claim 1:
An imaging device comprising:
an IR source (<NUM>);
a collimator (<NUM>) positioned downstream of the IR source (<NUM>);
an interferometer (<NUM>) positioned downstream of the collimator (<NUM>);
a sample compartment (13A) positioned downstream of the interferometer (<NUM>);
a detector (<NUM>) positioned downstream of the sample compartment (13A); and
an aperture controlling assembly (<NUM>) positioned between the sample compartment (13A) and the detector (<NUM>) and comprising:
a first plate (<NUM>) having a first plurality of circular plate apertures (<NUM>) extending therethrough;
a second plate (<NUM>) having a second plurality of rectangular plate apertures (<NUM>) extending therethrough, wherein the second plurality of rectangular plate apertures (<NUM>) includes four groups of rectangular plate apertures (<NUM>, <NUM>, <NUM>, <NUM>), wherein each group of rectangular plate apertures comprises a plurality of rectangular plate apertures of the same length, wherein each group has rectangular plate apertures of a different width from the other groups, wherein the plurality of rectangular plate apertures in the same group are of the same size ;
a first motor (<NUM>) operably connected to the first plate; and
a second motor (<NUM>) operably connected to the second plate, the first and second motors (<NUM>, <NUM>) configured to move the first plate (<NUM>) and the second plate (<NUM>) with respect to one another so as to align any one of the first plurality of circular plate apertures (<NUM>) with any one of the second plurality of rectangular plate apertures (<NUM>) to define a plurality of light beam apertures (<NUM>),
wherein for each group of rectangular plate apertures, the rectangular plate apertures (<NUM>) are positioned on the second plate (<NUM>) such that each rectangular plate aperture of the group of rectangular plate apertures is configured to align with any one of the circular plate apertures (<NUM>) in a different orientation.