Method and apparatus for determining the force applied to a sample in optical interrogation techniques

Abstract

An optical measurement system for inspecting a sample. The measurement system includes an internal reflection element, a stage, an optical assembly, a base, and a sensor. The internal reflection element has a contact surface. The stage is located below the internal reflection element. The stage and the internal reflection element are configured to apply a force to the sample. The optical assembly includes a light source and a light detector. The optical assembly is configured to scan the sample by directing source light from the light source toward the contact surface and detecting the source light optically interacting with the contact surface through the light detector. The base is configured to support the optical assembly and the internal reflection element. The sensor is mounted on the base and is configured to detect the force applied to the sample by the internal reflection element and the stage.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 222,525 (filed on July 16, 2021), the disclosure of which is incorporated herein by reference in its entirety for any and all purposes. Technical Field

[0003] The present disclosure relates generally to spectroscopy and, more particularly, to optical interrogation systems and methods for determining contact forces on a sample. Background Art

[0004] Attenuated total reflectance (ATR) is an optical interrogation technique often used in conjunction with infrared spectroscopy (e.g., Fourier transform infrared spectroscopy (FTIR)) that allows for direct examination of solid, liquid, or gaseous samples. Specifically, ATR exploits the total internally reflected light generated at the interface of a configured internal reflection element (IRE) and a coupled sample plane. In operation, a light beam (e.g., infrared light) passes through the IRE crystal in such a way that it is reflected at least once on the internal surface in contact with the sample. This reflection forms an evanescent wave that extends into the sample, typically up to about 2 microns, with the exact value being determined by the wavelength of the light, the angle of incidence and the refractive index of the IRE crystal, and the sample medium being interrogated. The reflected light beam, carrying spectral information of the sample, is then interrogated for analysis by, for example, a single pixel, linear array, or two-dimensional array detector.

[0005] The samples (primarily solid samples to be interrogated by ATR as an interrogation technique) can come in many different shapes and sizes. To achieve effective optical coupling, force is applied to such samples by a stage mechanism configured to provide close contact with optical components such as diamond, silicon or germanium (Ge) ATR elements. Conventional stages contain a pressure mechanism that includes machine screws, levers, slides and actuators to apply pressure to a given sample.

[0006] However, when performing a typical ATR measurement, in order to accurately control the signal-to-noise ratio in the ATR measurement, a reproducible and controllable force needs to be applied to the sample.

[0007] The above background discussion is intended only to assist the reader. It is not intended to limit the innovations described herein. Therefore, the above discussion should not be taken as indicating that any particular element of an existing system is not suitable for use with the innovations described herein, nor is it intended to indicate that any element is essential in implementing the innovations described herein. Summary of the invention

[0008] The ATR measurement system described herein satisfies the above needs to a large extent. The ATR measurement system enables low-resistance motion of the objective lens, ATR, and structures associated with the bracket on bearings. The system can be in contact with sensitive sensors (e.g., load cells, strain gauges) electrically attached to low-noise circuits and operational amplifiers. The range of the load sensor (and / or strain gauge) is limited, thereby achieving accurate and repeatable measurement of low forces. The deflection of the sensor is very small before failure, thereby maintaining optical alignment.

[0009] The ATR measurement system can measure the force and / or pressure at the ATR tip. The sensor can be combined with high precision low noise analog electronic circuits to enable users to measure force more accurately.

[0010] Conventional systems use less sensitive sensors that rely on additional forces applied to the stage that supports the sample and the weight of the sample. The strain should be designed to be low due to the need to limit deflection on the stage. This affects the percentage of strain that the strain gauge is able to measure. There may be linearity and accuracy issues with force measurements when exposed to low strains. Large strains may not allow for a rigid optical path when the sensor is applied to the upper assembly. Sensor setups are often run with the material at approximately 50% strain; these sensors are typically not linear or accurate at 10% strain. Therefore, high-precision sensors may be too flexible for microscopy applications, while more rigid sensor designs suitable for microscopy may not be accurate under typical ATR loads.

[0011] The ATR measurement system described herein includes a load sensor located on the optical side of the system, which is connected to the base. The system includes a hinge connection that essentially allows the sensor to measure almost all forces at the ATR contact point. The sensor has a limited measurement range, so the force being measured is within the measurement range. By applying a fixed, constant load to the stage supporting the sample (e.g., above), the entire load of the optical assembly can be supported by a fastener (e.g., from below). At this point, the hinged beam can be positioned relative to the sample (e.g., vertically), but it can be restored to the same position on the fastener. The sensor can be calibrated or zeroed. The sensor can be configured to repeatedly and accurately report the load applied to the sample by the ATR crystal during measurement.

[0012] According to one aspect of the present disclosure, a measurement system for inspecting a sample is provided. The measurement system may include an internal reflection element, a stage, an optical assembly, a base, and a sensor. The internal reflection element may include a contact surface configured to contact the sample. The stage may be located adjacent to the internal reflection element (e.g., axially below). At least one of the stage and the internal reflection element may be configured to apply a force to the sample when the sample is located on the stage and the contact surface is in contact with the sample. The optical assembly may include a light source and a light detector. The optical assembly may be configured to scan the sample by directing source light from the light source to the contact surface and detecting the source light optically interacting with the contact surface by the light detector. The base may be configured to support the optical assembly and the internal reflection element. The sensor may be mounted on the base and configured to detect a force applied to the sample by at least one of the internal reflection element and the stage.

[0013] According to another aspect of the present disclosure, a method for inspecting a sample with a measurement system is provided. The method may include: placing a sample on a stage; contacting the sample with a contact surface of an internal reflective element, the internal reflective element being positioned adjacent to the stage (e.g., axially above); applying a force to the sample with at least one of the stage and the contact surface of the internal reflective element; and detecting the force applied to the sample with a sensor. The sensor may be mounted on a base. The base may be configured to support an optical component adjacent to (e.g., vertically above) the stage. The optical component may include a light source and a light detector. The optical component may be configured to scan the sample by directing source light from the light source to the contact surface and detecting the source light optically interacting with the contact surface with the light detector.

[0014] This summary is provided to introduce in simplified form a selection of concepts further described in the detailed description below. This summary is not intended to identify the key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. In addition, the claimed subject matter is not limited to technical solutions that solve any or all of the shortcomings mentioned in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above summary and the following detailed description of exemplary embodiments of the present application will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the present application, exemplary embodiments of the present disclosure are shown in the accompanying drawings. However, it should be understood that the present application is not limited to the precise arrangements and means shown. In the accompanying drawings:

[0016] Figure 1The figure shows a top view of an ATR measurement system according to one aspect of the present disclosure.

[0017] Figure 2 Shows Figure 1 Side view of the ATR measurement system shown in .

[0018] Figure 3 FIG. 1 shows a schematic diagram of an ATR measurement system according to one aspect of the present disclosure.

[0019] Figure 4 A side schematic diagram of a portion of an ATR measurement system according to one aspect of the present disclosure is shown.

[0020] Figure 5 According to one aspect of the present disclosure, Figure 1 A close-up side view of the load measurement assembly of the ATR measurement system shown in FIG.

[0021] Figure 6 A schematic diagram of a controller according to one aspect of the present disclosure is shown.

[0022] Figure 7 A method of inspecting a sample using a measurement system according to one aspect of the present disclosure is illustrated. DETAILED DESCRIPTION

[0023] Certain terms used in this specification are for convenience only and are not limiting. The words "axial", "radial", "circumferential", "outward", "inward", "upper" and "lower" refer to directions in the referenced drawings. As described herein, when used to describe a size, shape, orientation, distance, spatial relationship or other parameter, the term "substantially" and its derivatives and words of similar meaning include the size, shape, orientation, distance, spatial relationship or other parameter, and may also include a range of 10% more and 10% less than the parameter, including a range of 5% more and 5% less than the parameter, a range of 3% more and 3% less than the parameter, and a range of 1% more and 1% less than the parameter. All ranges disclosed herein include the endpoints and can be independently combined (for example, the range of "from 2 grams to 10 grams" includes the endpoints, 2 grams and 10 grams and all intermediate values). This term includes the above-listed words, their derivatives and words of similar meaning.

[0024] In Fourier Transform Infrared (FTIR) spectroscopy, an unknown substance is illuminated with a broad spectrum of infrared light, which is absorbed by the sample of interest. The wavelengths illuminated by the light source range from approximately 0.7 microns to 25 microns. The intensity of the light as a function of wavelength is measured before and after interaction with the sample, and the absorbance due to the sample is calculated. Light is absorbed by the sample in different amounts at specific frequencies corresponding to the vibrational frequencies of the molecular bonds in the sample. Since the bonds are different for each molecule, the FTIR absorption spectrum is also different for each molecule. Therefore, a spectral "fingerprint" can be generated by recording the absorbance of light as a function of wavelength.

[0025] For a typical ATR / FTIR instrument, conventional pressure devices use drive screws, levers, and wedges to generate force and / or pressure on the material, and the mechanism requires manual movement by the user. Manual movement is one way to apply force, but the user (e.g., tester) can manipulate a joystick to raise the stage, or software can be used to raise the stage to a specific position relative to the internal reflective element (IRE). However, such conventional manual (e.g., knob-driven) movements of the mechanism tend to be large and awkward, and are also difficult to operate in a way that applies contact force repeatably or according to desired properties such as desired spectral features. When testing hard samples, where the force may only increase by a few microns, manual methods can be very difficult, time-consuming, or both to ensure that the interface pressure is at the preferred level.

[0026] Figure 1 and 2 A perspective view and a side view of an ATR measurement system 100 according to aspects of the present disclosure are shown. The measurement system 100 can include an optical assembly 101, a base 200, a load measurement assembly 300, and a manual slide mechanism 187 that can accurately position an ATR crystal. The base 200 can support the optical assembly 101 and the load measurement assembly 300. As further described herein, the load measurement assembly 300 can be connected to the optical assembly 101. The ATR crystal slider 187 can be positioned adjacent to (e.g., below) the optical assembly 101 and can be configured to fixedly position the ATR crystal to be aligned with a sample material 190 thereon (see Figure 4 As further described herein, the optical assembly 101 can be configured to optically interrogate the sample material 190.

[0027] Figure 3 FIG. 1 is a schematic diagram of an ATR measurement system 100 according to one aspect of the present disclosure. The measurement system 100 may include an optical assembly 101. The optical assembly 101 may include various optical components mounted on a base, such as Figure 1 and Figure 2The optical assembly can be located within the housing 156. The optical assembly 101 can include radiation sources 102 and 144, reflectors 104, 108, 110, 148, 118, 120, 120', 126, 126', 128, and 130, beam splitters 106 and 146, detectors and / or sensors 132 and 150, and an internal reflective element 122 (e.g., a prism). It should be understood that while a number of the reflectors 104, 108, 110, 148, 118, 120, 120', 126, 126', 128, and 130 are generally shown as being planar in design, the reflectors and / or other optical elements can include refractive optical elements (e.g., lenses), and non-planar reflective elements can also be configured to have other predetermined curvatures to provide Figure 3 For example, such elements may be configured to have concave curvature, convex curvature, parabolic curvature, elliptical curvature, or any general surface necessary to provide appropriate beam configuration along any portion of the beam path directed within system 100.

[0028] The optical assembly 101 may further include a shaft 112, a bushing 114, and an actuator 116 coupled to the reflector 110, as well as an electronic processor 134, an electronic display 136 (e.g., including a flat panel display element such as a liquid crystal display element, an organic light emitting diode display element, an electrophoretic display element, or another type of display element capable of touch screen operation), an input device 138, a storage unit 140, and a communication interface 142. The electronic processor 134 may be in electrical communication with the light detector 132, the storage unit 140, the communication interface 142, the display 136, the input device 138, the radiation sources 102 and 144, the detector 150, and the actuator 116 via communication lines 162a-i, respectively.

[0029] The system 100 can be configured to be used as an FTIR spectrometer during operation. It should be understood that the system 100 can be used for other types of spectra, including, for example, ultraviolet, visible light, Raman or other types of spectra. Under the control of the processor 134, the system 100 can provide light 168 through the light source 102, which can be removable for easy replacement. The light 168 can include radiation from the light source 102, which can include a radiation source. The radiation 168 can be directed by the reflector 104 to be incident on the beam splitter 106, which can be configured as a beam splitting optical element 106a and a phase compensation plate 106b so that the received radiation 168 can be split into two beams. Using such a configuration, an interferometer (e.g., a Michelson-type interferometer) can be formed, in which the first beam 170 is reflected from the surface of the beam splitter 106, propagates along a beam path parallel to the arrow 171, and is incident on the fixed reflector 108. Thereafter, the fixed mirror 108 may reflect the first light beam 170 in the opposite direction so that it is then directed toward the beam splitter 106. The second light beam 172 may be transmitted through the beam splitter 106 and propagate along a beam path parallel to the double arrow 173. The second light beam 172 may be incident on the first surface 110a of the movable mirror 110 and thereby also directed toward the beam splitter 106 upon reflection.

[0030] The first and second light beams 170 and 172 may be combined by a configuration of the beam splitter 106 and associated optical devices, which spatially overlap the beams to form a beam of modulated infrared radiation beam 174 (by operation of a configured interferometer) and directed toward the reflector 118. Thereafter, the reflectors 118, 120, 120' may direct the modulated infrared radiation beam 174 toward the internal reflective element 122. Once entering the internal reflective element 122 (typically configured as a prism), the modulated infrared radiation beam 174 may be directed toward the ATR tip or contact surface 122a of the internal reflective element 122. The contact surface 122a of the internal reflective element 122 may be positioned adjacent to (e.g., above) a sample 190 of interest. In some cases, the sample 190 may include irregularities in the surface configuration (e.g., powder). When the modulated infrared light 174 is incident on the contact surface 122a, a portion of the radiation of the modulated infrared light 174 may be directed through the contact surface 122a to the sample material 190 via a desired evanescent wave effect (see Figure 4 As part of this effect, the sample 190 may desirably absorb a portion of the modulated infrared light 174 that is representative of the structure of the sample material 190 and therefore indicative of the properties of the sample material.

[0031] The totally internally reflected portion 176 of the modulated infrared light 174 can include a reduced amount of modulated radiation that is not absorbed by the sample 190. The reflected light beam 176 can be directed through a desired surface of the internally reflective element 122 and can then be directed by, for example, mirrors 126', 126, 128, and 130 for interrogation by the system 100 via detection by the light detector 132. In particular, under the control of the processor 134, the light detector 132 can be configured to measure one or more characteristics of the sample 190 based on the reflected radiation in the light beam 176.

[0032] As described above, the mirrors 108 and 110 are configured to advantageously form an interferometer together with the beam splitter 106. In operation, by translating the mirror 110 in a left-right direction (e.g., double arrow 164) before each measurement, an interference pattern containing information (e.g., sample absorption information) can be formed through multiple measurements of the radiation in the reflected beam 176. The processor 134 can be configured to apply one or more mathematical transforms (e.g., Fourier transforms) to the interference pattern to obtain the sample absorption information.

[0033] The reflector 110 can be coupled to the shaft 112, the bushing 114 and the actuator 116. The shaft 112 can move freely within the bushing 114, and a viscous fluid is usually provided between the shaft 112 and the bushing 114 to achieve relative movement therebetween. Thus, when the actuator 116 receives a control signal from the processor 134 via the communication line 162i, the reflector 110 can move.

[0034] To measure the position of the reflector 110, the light source 144, the beam splitter 146, the reflector 148, and the detector 150 can be configured to measure the position of the reflector 110. These components can be arranged to form a second interferometer (e.g., a Michelson-type interferometer). During the operation of the reflector position measurement, the light source 144 (e.g., a monochromatic emission source (laser)) can receive a control signal from the processor 134 via the communication line 162g and can generate a radiation beam 178. As an example of a desired light source, the light source 144 can be a configured vertical cavity surface emitting laser (VCSEL) that generates radiation having a central wavelength of 850nm. However, it should be understood that the source 144 can also include a variety of other sources, such as laser diodes, light emitting diodes, etc., which can have radiation between 400nm and about 1200nm.

[0035] The beam 178 may be incident on the beam splitter 146, which may split the radiation beam 178 into a first beam 180 and a second beam 182. The first beam 180 may be reflected from a surface of the beam splitter 146 and may be incident on the second surface 110b of the reflector 110. The second surface 110b may be positioned relative to the first surface 110a of the reflector 110. The first beam 180 may be reflected from the surface 110b and return to the beam splitter 146. The second beam 182 may be emitted through the beam splitter 146, reflected by the reflector 148, and return to the beam splitter 146. The beam splitter 146 may combine (e.g., spatially overlap) the reflected beams 180 and 182, and the spatially overlapped beam 184 may be directed to the detector 150. The detector 150 may receive a control signal from the processor 134 via the communication line 162k, and may be configured to determine the intensity of the combined beam 184. The combined beam 184 may provide an interference pattern containing desired optical position information. Thus, monitoring beam 184 can accurately determine the position (and velocity and tilt, if necessary) of mirror 110 by counting the peaks and valleys in the amplitude of beam 184.

[0036] In one aspect, the processor 134 can compare the absorption information with reference information (e.g., reference absorption information) stored in the storage unit 140 to determine the characteristics of the unknown sample. For example, after Fourier transforming the received reflected light beam 176, the processor 134 can determine whether the absorption information of the sample matches any one or more of a plurality of sets of reference absorption information for a plurality of substances stored as database records in the storage unit 140 or even from a database remotely located via wireless communication.

[0037] If a match is found (e.g., the sample absorption information and the reference information for a particular substance are sufficiently consistent), the sample 190 is considered to be identified by the processor 134. The processor 134 can send an electronic signal along the communication line 162d to the display 136, which indicates to the system operator that the identification of the sample 190 was successful and provides the name of the identified substance. If the processor 134 does not find a match between the sample absorption information and the reference information, the processor 134 can send an electronic signal to the display 136, which indicates to the system operator that the sample 190 was not successfully identified, or that effective optical coupling was not provided between the ATR contact surfaces 122a due to, for example, insufficient force applied by the contact member 191.

[0038] The communication interface may receive and send signals from / to the processor 134 via the communication line 162c. The communication interface 142 may include a wireless transmitter / receiver unit that may be configured to transmit signals from the processor 134 to other devices, and to receive signals from other devices and transmit received signals to the processor 134. For example, the communication interface 142 may allow the processor 134 to communicate with other devices via a wireless network including multiple devices connected to the network and / or via a direct connection with another device. The processor 134 may establish a secure connection (e.g., an encrypted connection) to one or more devices to ensure that signals can only be sent and received by devices approved for use on the network.

[0039] The light source 102 can be configured as a replaceable component. The light source 102 can include a broadband radiation source configured to provide infrared radiation, so that the system 100 can operate as an infrared spectrometer. The infrared radiation provided by the source 102 can include a wavelength distribution with a central wavelength of about 10 microns. Typically, the light source 102 can include a variety of light sources known to those skilled in the art, including a heated infrared source selected from any custom or conventional known light sources used in the art, such as but not limited to wires, metals, or ceramic elements that are heated to emit a continuous light radiation band.

[0040] Figure 4 A side view of a stage or platform 186 and an internal reflective element 122 according to one aspect of the present disclosure is illustrated. The stage 186 can be positioned adjacent to (e.g., below) the optical assembly 101 and can be configured to support a sample material 190 thereon. The internal reflective element 122 can include a contact surface 122a positioned to contact the sample 190. As shown, the sample 190 can include a powder represented by a circle. It should be understood that the sample 190 can include a solid or a liquid. Light from the light source 102 can enter the internal reflective element 122 and reflect from the surface 122b to the contact surface 122a, and can exit the internal reflective element 122 by reflecting from the surface 122c.

[0041] The edge of the internal reflective element 122 opposite the contact surface 122a can be supported (e.g., from above relative to the platform 186) and mounted directly or indirectly to the housing 156. The internal reflective element 122 can be rigidly mounted so that movement of the internal reflective element 122 can also cause the optical assembly 101 to move. A coating (not shown) such as a metal (e.g., gold) can be applied to the internal reflective element 122 to achieve a stable coupling with the bottom of the housing 156, which can further provide support for the internal reflective element 122 (e.g., from above). The support provided by the housing 156 can enable the internal reflective element 122 to withstand significant external forces during operation without being displaced from its mounted position.

[0042] The force assembly 250 can be connected to the stage 186 (e.g., from below relative to the optical assembly 101). The force-applying assembly 250 can include an actuator 202 and a translation member 205. The actuator 202 can include, for example, a motor (such as a DC motor) or a solenoid, an electromagnetic solenoid, or other type of force actuator that can be moved in a controlled manner (such as a piezoelectric drive mechanism, a linear motor, a rotary motor, a pneumatic or hydraulic actuator, etc.). The translation member 205 can be connected to the stage 186 to control the movement of the stage 186 in the vertical directions V and V' and / or the rotational direction (not labeled). The translation member 205 can include a screw mechanism, a cam, or other mechanism to control the linear and / or rotational movement of the stage 186. In one aspect, the stage 186 and the sample 190 can be positioned adjacent to (e.g., vertically below) the internal reflective element 122.

[0043] During interrogation, the operator can control the actuator 202 to translate the stage 186 in the vertical direction V so that the sample 190 contacts the contact surface 122a of the internal reflective element 122. The stage 186 can be controlled to be raised and / or rotated into position. When the sample 190 contacts the contact surface 122a, at least one of the stage 186 and the internal reflective element 122 can apply a force to the sample 190. The movement of the stage 186 can bring the contact surface 122a into close contact with the sample material 190 to achieve efficient coupling of the evanescent wave and improve the signal-to-noise ratio in the measurement of the reflected radiation beam 176. The housing 156 of the optical assembly 101 can ensure that the internal reflective element 122 remains in the same position on the stage 186.

[0044] The contact force applied by the stage 186 and / or the internal reflective element 122 to the sample 190 can be a desired fixed force that is a user-selectable force, or a desired force that is controlled by spectrometer feedback based on spectrometer characteristics of the sample 190. For example, a user can select a fixed force to be applied, and the stage 186 can be controlled to apply the fixed force to the sample 190. Alternatively, the force applied by the stage 186 and / or the internal reflective element 122 to the sample 190 can depend on, for example, the light detector 132 at the detection end of the beam path (see Figure 3) feedback. When force is applied to sample 190, optical assembly 101 can simultaneously and continuously query the signal strength provided by light detector 132. If the signal strength (e.g., sample spectral feature strength) provides a reasonable signal, stage 186 can be controlled to stop and the force applied to sample 190 can be maintained. If the signal is unreasonable, stage 186 can continue to increase the force and / or can apply pressure to sample 190 until the maximum allowable force is applied or until an acceptable signal strength is obtained. This operation stops stage 186 from moving once there is sufficient contact force and / or pressure for a reasonable signal. It should be understood that other operations (e.g., movement of an internal reflective element) can be used to apply force and / or pressure to sample 190.

[0045] Figure 5 A close-up side view of a load measurement assembly 300 connected to a base 200 according to one aspect of the present disclosure is shown. The load measurement assembly 300 can be further connected to a front end assembly 302. The front end assembly 302 can include a plate member 304 rigidly connected to the base 200. The connection between the front end assembly 302 and the base 200 can define a cantilever connection. The plate member 304 can extend from the base 200 in a direction substantially perpendicular to the vertical directions V and V'. The plate member 304 can be configured to deflect in the vertical directions V and V'. The plate member 304 can include steel, aluminum, titanium, a composite material, or a polymer material. The plate member 304 can be rigidly fixed to and at least partially support the optical assembly 101. The optical assembly 101 and the internal reflective element 122 can define a fixed constant load adjacent to (e.g., above) the sample 190. It should be understood that the plate member 304 may include more than one plate, a beam, multiple beams and / or other structures that are configured to support the optical component 101 and are further configured to deflect based on the force and / or pressure applied to the internal reflective element 122.

[0046] The load measurement assembly 300 may include a sensor 306, a deflection assembly 308, and a controller 310 (see Figure 6). The deflection assembly 308 can be mounted to the base 200. The sensor 306 can be mounted to the deflection assembly 308. The controller 310 can be located on the base 200 or other structure of the ATR measurement system 100. Alternatively, the controller 310 can be located at a location remote from the measurement system 100 and configured to communicate with the measurement system 100 via a communication interface (not shown). At least a portion of the deflection assembly 308 can be configured to deflect based on the force and / or pressure applied to the sample 190 by the internal reflective element 122 and / or the stage 186. As further described below, the sensor 306 can be configured to detect the deflection of the deflection assembly 308. The sensor 306 can be further configured to provide a signal indicating the deflection of the deflection assembly 308 to the controller 310. The controller 310 can be configured to determine the force and / or pressure applied to the sample 190 based on the signal indicating the deflection received from the sensor 306.

[0047] The deflection assembly 308 may include a projection member 312, a hinged beam 314, and a support member 316. It should be understood that the deflection assembly 308 may also include a plate member or beam 304, or other structures configured to facilitate the load measurement described herein. The support member 316 may be fixedly connected to the base 200 by a fastener 318. The fastener 318 may include, for example, a screw, a rivet, a clamp, and / or other types of fasteners. The support member 316 may include a hinge support surface 320, which is configured to connect a hinge 322 thereon. The support member 316 may include a first hole and a second hole (not visible in the figure) extending through (or at least partially through) the support member 316 to the hinge support surface 320. In one aspect, the first and second holes may both extend in substantially horizontal directions H and H'. The horizontal directions H and H' are substantially perpendicular to the vertical directions V and V'. The first hole may be configured to receive a hinged beam retaining element 324. As further described below, the hinged beam retaining element 324 can be used to adjust the position of the hinged beam 314. The second hole can be configured to receive a first bearing element 326. As further described below, the first bearing element 326 can be configured to substantially prevent rotational movement of the hinged beam 314.

[0048] The support member 316 can further include a projected support surface 328 defining a third hole (not visible). The third hole can be configured to receive a second bearing element 330. As further described below, the second bearing element 330 can be configured to substantially prevent rotation of the projection member 312. In one aspect, the projected support surface 328 can be substantially parallel to the hinge support surface 320.

[0049] The articulated beam 314 may include a rear articulated surface 332 and a front articulated surface 334. In one aspect, the rear articulated surface 332 may be substantially parallel to the front articulated surface 334. The rear articulated surface 332 may be connected to the hinge 322 such that the articulated beam is articulated to the support member 316. The articulated beam 314 may be configured to rotate about the hinge 322 relative to the support member 316. The hinge 322 may include, for example, a pin joint or other type of hinge. It should be understood that the hinge 322 may include (or be replaced by) another component configured to allow rotation, such as a flexure beam, a flexure element, or other similar component. In one aspect, the rotation of the articulated beam 314 about the hinge 320 may be substantially perpendicular to the vertical directions V and V'. During operation, the rear articulated surface 332 may be configured to abut against the first bearing element 326 and / or the articulated beam retaining element 324 connected to the support member 316.

[0050] The sensor 306 can be connected to the front hinge surface 334 of the hinged beam 314, so that the sensor 306 is hingedly connected to the base 200 through the hinge 322. The sensor 306 can be configured to abut the projection surface 336 of the projection member 312. The sensor 306 can be configured to sense the movement and / or deflection of the projection member 312. The sensor can include a load cell, a strain gauge, a force sensitive resistor, or other type of force sensor or transducer configured to detect a load.

[0051] The projection member 312 can be fixedly connected to the plate member 304 of the front end assembly 302 by a fastener 338. The projection member 312 can extend from the plate member 304 at least partially in the vertical direction V. The projection member 312 can include a projection surface 336. The projection surface 336 can face the front hinge surface 334 hinge beam 314. During operation, movement and / or deflection of the projection surface 336 can be sensed by the sensor 306. As further described below, the projection surface 336 can be further configured to abut against a second bearing element 330 positioned within the support member 316.

[0052] Figure 6A schematic diagram of a controller 310 according to one aspect of the present disclosure is shown. As shown, the controller 310 may include a processor 350 and a memory 352. It should be understood that the controller 310 may also include a processor 134, a display 136, a storage unit 140, a communication interface 142, or other computing components. The memory 352 may store data provided to the controller 310 from the sensor 306, which indicates the deflection of the deflection assembly 308. The memory 352 may also store executable code, which includes an algorithm for determining the force and / or pressure applied to the sample 190 by the internal reflective element 122 and / or the stage 186. The memory 352 may include a random access memory (RAM), or a read-only memory (ROM), or both. The controller 310 may be connected to the actuator 202 of the force assembly 200. The controller 310 may send a signal to the actuator 202 to adjust the height of the stage 186 to affect the force and / or pressure applied to the sample 190.

[0053] Figure 7 1 is a flow chart describing a method 400 for inspecting a sample 190 using an ATR / FTIR measurement system 100 according to one aspect of the present disclosure. In step 402, the load measurement assembly 300 may be positioned. Figure 5 , positioning the load measurement assembly 300 can include rotating the hinged beam 314 about the hinge 322 until the sensor 306 contacts the projection surface 336 of the projection member 312. The hinged beam 314 can be rotated using the first bearing element 326 to apply a force to the rear hinge surface 332. Once the sensor 306 is positioned, the first bearing element 326 can be locked to substantially prevent the hinged beam 314 from rotating in a direction away from the projection surface 336 of the projection member 312. The sensor 306 can be approximately zeroed so that the initial force detected by the sensor is approximately zero.

[0054] It should be understood that when the optical assembly 101 and the internal reflective element 122 are fixedly connected to the front end assembly 302, 304 may initially deflect downward in the vertical direction V' due to the load (e.g., weight) of the optical assembly 101 and the internal reflective element 122. To compensate for this initial deflection, the sensor 306 is positioned to contact the projection member 312 as previously described.

[0055] In step 404, the sample 190 can be positioned on the stage 186. In one aspect, the sample 190 can be positioned toward the center of the stage 186 and at least partially below the internal reflective element 122. After the sample 190 is placed on the stage 186, in step 406, the stage 186 can be raised in a vertical direction V until the internal reflective element 122 contacts the sample 190. In one aspect, after the internal reflective element 122 has contacted the sample 190, the sensor 306 can be again (or initially) approximately zeroed.

[0056] In step 408, a contact force and / or pressure may be applied to the sample 190 by the stage 186 against the ATR tip 122a of the internal reflective element 122. The force and / or pressure may be applied to the sample 190 by repositioning (e.g., raising) the stage 186 by the actuator 202. As described above, the contact force and / or pressure applied to the sample 190 may include a desired force and / or pressure selected by a user, controlled by signal strength feedback, or a force determined by another method. In one aspect, after the internal reflective element 122 has applied an initial force to the sample 190, the sensor 306 may be again (or initially) approximately zeroed.

[0057] In step 410, the sensor 306 can detect the initial force and / or pressure applied to the sample 190 by the stage 186 and the internal reflective element 122. The detected initial force and / or pressure can correspond to the required contact force and / or pressure described above. The detected initial force and / or pressure can be stored in the storage unit 140 and / or the memory 352 of the controller 310.

[0058] When a force is applied to the sample 190, the sensor 306 detects the force based on the deflection of the optical assembly 101 and the internal reflective element 122. The force applied to the sample by the internal reflective element 122 can be substantially in the vertical direction V'. As the height of the stage 186 is repositioned (e.g., raised) and the force applied to the sample 190 increases, the internal reflective element 122 and the optical assembly 101 can deflect upward along the vertical direction V. The deflection of the optical assembly 101 in the vertical direction V can cause the front end assembly 302 to deflect along the vertical direction V. For example, the plate member 304 can rotate around the rigid connection with the base 200 (e.g., cantilever rotation / bending). The deflection of the plate member 304 can cause the projection member 312 to deflect in a direction that is angularly offset from the vertical direction V. In one aspect, the projection member deflects substantially along the horizontal direction H. The deflection of the projection member 312 can cause the projection surface 336 to apply a deflection force to the sensor 306. The controller 310 may use the deflection force detected by the sensor 306 to determine the force applied to the sample 190 by the stage 186 and the internal reflective element 122 .

[0059] The sensor 306 can be configured to detect deflections of the projection surface 336 up to about 30 microns. It should be understood that the sensor 306 can be configured to detect deflections greater than about 30 microns. For example, the sensor can be located at different locations on the measurement assembly 300 to measure deflections of one or more different components of the measurement assembly 300. The deflection of the projection member 312 can be limited by the second bearing element 330 on the support member 316. The second bearing element 330 can prevent damage to the sensor 306 due to excessive deflection of the projection member 312. For example, instead of applying all of the force applied to the projection member 312 to the sensor 306, at least a portion of the applied force is applied to the second bearing element 330.

[0060] In step 412, the sample 190 may be scanned by the optical assembly 101 to identify the sample 190. The scanning step includes directing source light from the light source 102 to the contact surface 122a of the internal reflective element 122. The source light 102 may optically interact with the contact surface 122a. The light detector 132 detects the source light 102 optically interacting with the contact surface 122a.

[0061] As a result of the force being applied to the sample 190, the sample 190 may deform and / or degrade. The degradation may affect the contact force and / or pressure applied by the ATR tip 122a on the sample 190. For example, after scanning, the contact pressure may be reduced, thereby affecting the measurements made during the continuous scan of the sample 190. As described below, the force applied by the contact member 191 to the sample 190 may be adjusted before the optical assembly 101 performs a continuous scan.

[0062] After the scanning step, in step 412, the sensor 306 can detect the resultant force and / or pressure applied to the sample 190 by the ATR tip 122a. The sensor 306 can send a signal indicating the resultant force to the controller. The resultant force can be compared with the initial force to determine whether the resultant force is different from the initial force. The comparison step can be performed by the processor 350 or another processor of the controller 310. If the resultant force is different from the initial force, the controller 310 can send a signal to the actuator 202 to adjust the force applied to the sample 190. The actuator 202 can increase the height of the stage 186 to adjust the upper force applied to the sample 190 from the resultant force to the initial force.

[0063] The position of sensor 306 on base 200 can ensure that the load measurement is independent of the travel of stage 186. The load applied to the ATR can be substantially equal to the load on sample 190. The position of stage 186, sample uniformity, sample weight, and stage control can all affect the load measurement. When sensor 306 is positioned adjacent to stage 186 and sample 190 (e.g., above it), and when the supporting weight of the articulated structure including optical assembly 101 is zeroed, sensor 306 can immediately sense any force applied to the optical articulated structure along the vertical direction V.

[0064] In one aspect, the alignment of the optics can be decoupled from the preload of the sensor 306. The hinge 322 can be adjusted to align the objective lens on the tilt axis. Once completed, the sensor can be positioned (e.g., lowered) onto the carrier with minimal preload. In this configuration, the sensor 306 can be essentially the only resistance to the ATR load.

[0065] It should be understood that the above description provides examples of the disclosed systems and methods. However, it is contemplated that other embodiments of the present disclosure may differ in detail from the above examples. For example, any embodiment disclosed herein may be combined with features disclosed with respect to any other embodiment disclosed herein. All references to the present disclosure or its examples are intended to reference the specific examples being discussed at the time and are not intended to imply any more general limitation on the scope of the present disclosure. All distinctions and derogatory language regarding certain features are intended to indicate a lack of preference for those features, but unless otherwise stated, they are not completely excluded from the scope of the present disclosure.

[0066] A person skilled in the art will readily appreciate that, based on the present disclosure, it is possible to utilize processes, machines, manufacture, material compositions, devices, methods, or steps that currently exist or will be developed later and that perform substantially the same functions as the corresponding embodiments described herein or achieve substantially the same results as the corresponding embodiments described herein.

Claims

1. A measurement system for inspecting a sample, the measurement system comprising: an internal reflective element having a contact surface configured to contact the sample; a stage positioned adjacent to the internal reflective element, wherein at least one of the stage and the internal reflective element is configured to apply a force to the sample when the sample is positioned on the stage and the contact surface is in contact with the sample; an optical assembly including a light source and a light detector, wherein the optical assembly is configured to scan the sample by directing source light from the light source toward the contact surface and detecting, by the light detector, the source light that optically interacts with the contact surface; a base configured to support the optical assembly and the internal reflective element; as well as A sensor is mounted to the base, the sensor being configured to detect a force applied to the sample by at least one of the internal reflective element and the stage.

2. The measurement system of claim 1, wherein the sensor comprises a load sensor. The measurement system of claim 1 , wherein the sensor comprises a strain gauge.

4. The measurement system of claim 1 , wherein the force is a sample force, and wherein the sensor is in contact with the optical component such that the sample force is detected based on a deflection force applied to the sensor from the optical component, the deflection force being a result of the sample force applied to the sample. 5 . The measurement system of claim 4 , wherein the sensor is configured to detect a deflection of the optical component when the sample force is applied to the sample. The measurement system of claim 5 , wherein the deflection is less than about 30 microns.

7. A measurement system according to claim 4, wherein the sample force applied to the sample by at least one of the internal reflective element and the stage is in a substantially perpendicular direction parallel to an axis defined by the internal reflective element and the stage, and wherein the detected deflection is angularly offset from the sample force applied to the sample.

8. The measurement system according to claim 5, further comprising: a deflection assembly coupled between the base and the optical assembly, wherein the deflection assembly includes a light beam extending at least partially in a horizontal direction perpendicular to an axis defined by the internal reflective element and the stage, and a projection extending from the light beam at least partially in a vertical direction parallel to the axis defined by the internal reflective element and the stage, the sensor including a load sensor, wherein the deflection of the optical assembly deflects the light beam at least partially in the vertical direction and deflects the projection at least partially in the horizontal direction to apply the deflection force to the load sensor through the projection.

9. The measurement system of claim 1, wherein the sensor is hingedly connected to the base.

10. The measurement system of claim 1, wherein the stage is configured to translate axially to adjust a position of the stage relative to the internal reflective element.

11. The measurement system according to claim 10, further comprising: An actuator is configured to adjust a force applied to the sample by at least one of the stage and the internal reflective element.

12. The measurement system of claim 11, wherein before the scanning, an initial force is applied to the sample by at least one of the stage and the internal reflective element, and wherein after the scanning, a resultant force is applied to the sample by at least one of the stage and the internal reflective element, wherein the sensor is further configured to detect the initial force and the resultant force, the system further comprising: A controller is configured to receive a signal indicative of the detected resultant force from the sensor, wherein the controller is further configured to control the actuator to adjust the force applied to the sample by at least one of the stage and the internal reflective element from the resultant force to the initial force.

13. A method for inspecting a sample using a measurement system, the method comprising: Place the sample on the stage; contacting the sample via a contact surface of an internal reflective element, the internal reflective element being positioned adjacent to the stage; applying a force to the sample with at least one of a contact surface of the stage and the internal reflective element; The force applied to the sample is detected by a sensor, The sensor is mounted on a base, the base is configured to vertically support an optical assembly above the stage, the optical assembly includes a light source and a light detector, wherein the optical assembly is configured to scan the sample by directing source light from the light source toward the contact surface and detecting the source light optically interacting with the contact surface through the light detector.

14. The method of claim 13, wherein the internal reflective element and the optical assembly define a fixed constant load axially above the sample relative to an axis defined by the internal reflective element and the stage.

15. The method according to claim 13, further comprising: After the step of contacting the sample, the sensor is zeroed so that the initial force detected by the sensor is approximately zero.

16. The method according to claim 13, further comprising: The stage is moved toward the internal reflective element to apply a force to the sample.

17. The method of claim 13, wherein the force is a sample force, and wherein the method further comprises applying a deflection force to the sensor, wherein the deflection force is applied to the sensor by the optical component as a result of the sample force applied to the sample.

18. The method according to claim 17, further comprising: When the sample force is applied to the sample, a deflection of the optical assembly is detected by the sensor.

19. A method according to claim 18, wherein the sample force applied to the sample by at least one of the internal reflective element and the stage is substantially perpendicular to an axis defined by the internal reflective element and the stage, and wherein the detected deflection is angularly offset from the sample force applied to the sample.

20. The method of claim 13, further comprising: scanning the sample through the optical assembly, wherein an initial force is applied to the sample prior to the scanning step; After scanning the sample, detecting, by the sensor, a sample resultant force applied to the sample by at least one of the stage and the internal reflective element; The force applied to the sample by at least one of the stage and the internal reflective element is adjusted from the resultant force to the initial force.

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