Fixture and method for optical alignment in a system for measuring the surface of a contoured glass sheet - Patent Application 20070122999

Abstract

The optical inspection system includes a fixture supporting the glass sheet, the fixture having optical fiducials. An ultraviolet laser and associated optics form a planar laser sheet that intersects the surface of the glass sheet, causing the surface to fluoresce and form visible wavelength lines thereon. A camera has an image sensor for detecting the optical fiducials and the visible wavelength lines across at least a portion of the width of the sheet. The control system is configured to (i) image the optical fiducials on the fixture, (ii) define an optical reference coordinate system from the imaged optical fiducials, (ii) receive a mathematical model of the glass sheet in a model coordinate system, and (iii) relate the optical reference coordinate system to the model coordinate system via at least one transformation. Methods of using the non-contact optical inspection system are also provided.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Patent Application Serial No. 17 / 884,116, filed August 9, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] Various embodiments relate to a fixture and method for using the fixture in a system for optically measuring the surface of a contoured glass sheet. [Background technology]

[0003] Manufacturers of glass sheets, particularly those formed into various curved shapes for use as automobile windshields, backlights, and sidelights, are interested in measuring and evaluating the surface of the glass sheets. Manufacturers may wish to determine whether the glass sheets are within predetermined dimensional specifications. Manufacturers may also wish to measure and evaluate the amount of optical distortion due to reflections in the formed sheets that may be perceived by an external observer or a human observer, such as a driver or passenger in a vehicle in which the glass may be installed as a windshield, backlight, or sidelight. For example, metrics and optical distortion thresholds are becoming increasingly stringent with the increasing use of technologies such as head-up displays in vehicle applications.

[0004] As part of measuring or gauging a glass sheet, it may be necessary to determine the position of the glass sheet within a scanning system. The use of conventional glass sheet support fixtures may not work with optical inspection systems that employ non-contact measurement or gauging, and the optical inspection system may not be able to precisely and / or accurately determine the position of the glass sheet without the use of calibrated fixtures. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic diagram illustrating a glass sheet inspection system in one embodiment. [Figure 1A] FIG. 2 is a schematic diagram of an optical inspection subsystem used in the glass sheet inspection system of FIG. 1. [Figure 2] 2 shows a flowchart of a method for optically aligning a fixture for measuring glass sheets using the optical inspection system of FIG. 1. [Figure 3] 2 is a perspective view of a fixture for use with the inspection system of FIG. 1 without the glass sheet in one embodiment. [Figure 4] FIG. 4 is a perspective view of the fixture of FIG. 3 with a glass sheet. [Figure 5A, 5B, 5C] 5A, 5B, and 5C are schematic diagrams of fixtures for the system of FIG. 1 for calibration of optical coordinates for various configurations of the system of FIG. [Figure 6A] FIG. 6A illustrates one or more methods for correlating optical, CMM, and CAD coordinate systems for use in the system of FIG. 1 and the method of FIG. [Figure 6B] FIG. 6B illustrates one or more methods for correlating the optical coordinate system, the CMM coordinate system, and the CAD coordinate system for use in the system of FIG. 1 and the method of FIG. [Figure 6C] FIG. 6C illustrates one or more methods for correlating the optical coordinate system, the CMM coordinate system, and the CAD coordinate system for use in the system of FIG. 1 and the method of FIG. [Figure 6D] FIG. 6D illustrates one or more methods for correlating the optical coordinate system, the CMM coordinate system, and the CAD coordinate system for use in the system of FIG. 1 and the method of FIG. [Figure 7] 10 is a perspective view of a fixture for use with the inspection system of FIG. 1 and the method of FIG. 2 according to another embodiment, without the glass sheet. [Figure 8] FIG. 8 is a cross-sectional perspective view of the fixture of FIG. 7 with a glass sheet. [Figure 9]3 is a perspective view of a fixture for use in the inspection system of FIG. 1 and the method of FIG. 2 according to yet another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0006] Where necessary, detailed embodiments of the present disclosure are provided herein; however, it should be understood that the disclosed embodiments are merely exemplary and may be embodied in various alternative forms. The figures are not necessarily to scale, and some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be construed as limiting, but merely as a representative basis for teaching those skilled in the art how to employ the present disclosure in various ways.

[0007] Any circuit or other electrical device disclosed herein may include any number of microprocessors, integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other suitable variations thereof), and software that cooperate with each other to perform the operations disclosed herein. Additionally, any one or more of the electrical devices disclosed herein may be configured to execute a computer program embodied in a non-transitory recording medium that is programmed to perform any number of functions as disclosed herein.

[0008] 1 illustrates a glass sheet optical inspection system 10 under inspection. One example of a subsystem for use with the system 10 and fixture 14 of the present disclosure is described in PCT Patent Application Serial No. PCT / US19 / 43180, filed July 24, 2019, entitled "System And Method For Measuring A Surface In Contoured Glass Sheets," the disclosure of which is incorporated herein by reference in its entirety. In other examples, other non-contact optical inspection systems can be used with the present disclosure.

[0009] The inspection system 10 includes a conveyor 12 that transports a glass sheet G, also referred to as a glass panel G, in a first direction generally parallel to a first dimension of the glass sheet. In the illustrated example, the contoured glass sheet G is a generally trapezoidal vehicle windshield or backlight having a first dimension (alternatively referred to as a height) that is a relatively smaller dimension and a second dimension (alternatively referred to as a width) that is a relatively larger dimension. The glass sheet G has a thickness in a third dimension, which is smaller than the width and height. The glass sheet G is curved about one or more axes of curvature generally parallel to the first direction. In other examples, the glass sheet G may have other axes of curvature, be provided as a flat or substantially flat sheet, or have other shapes.

[0010] Conveyor 12 may be a single conveyor dedicated solely to transporting glass sheets G through inspection system 10, which may be configured and / or operated as a standalone optical inspection system. In other examples, conveyor 12 may be one of a series of conveyors transporting glass sheets through various process stations, such as heating, forming, annealing, or tempering stations found in typical automotive, architectural, and / or solar glass sheet manufacturing systems. Conveyors for glass sheets G may be provided by a variety of technologies, such as roller, air float, or belt conveyors, positioners, and robotic arms, to handle the glass in the disclosed manner. It should also be understood that multiple conveyors (each of which may be independently controlled) may be provided to move glass sheets through different processing stations at speeds that efficiently manage the flow and processing of glass sheets throughout system 10. Alternatively, inspection system 10 may be provided as a separate, independent system or apparatus without a conveyor.

[0011] The inspection system 10 may include a fixture 14 for the glass sheet G. The fixture 14 supports and positions the glass sheet G thereon. The fixture 14 may provide precise and accurate positioning of the glass sheet G. A fixture for use with the system of FIG. 1 is described in further detail below with reference to FIGS. 3-4 and 7-9.

[0012] Inspection subsystem 16 may be configured to translate relative to sheet G and fixture 14, for example, with inspection subsystem 16 mounted to a conveyor system and / or fixture 14 mounted to conveyor system 12. Inspection subsystem 16 includes optical elements configured to scan the surface of glass sheet G based on relative movement of inspection subsystem 16 with respect to fixture 14.

[0013] Inspection subsystem 16 may be used to measure the surface of the glass sheet, and may further be used to gage the sheet, measure small surface curvature defects in the sheet, and / or measure optical distortion due to reflection. In one embodiment, inspection subsystem 16 for use with system 10 and fixture 14 of FIG. 1 is described with reference to FIG. 1A.

[0014] According to one embodiment, the inspection subsystem 16 is a non-contact optical system having one or more cameras or other detectors for imaging or otherwise detecting light used to measure and / or gauge the glass sheet G.

[0015] Referring to FIGS. 1 and 1A and further non-limiting examples, subsystem 16 includes a detector 30, such as a camera, and a light source 40, such as a laser. Detector 30 may be a single camera or multiple cameras imaging different areas of glass sheet G. In a multi-camera system, the areas imaged by the cameras may or may not overlap. According to one embodiment, subsystem 16 includes a laser 40 or other light source having a wavelength selected at least in part based on the optical properties of glass sheet G. The light source can output light in the visible or non-visible wavelength range, e.g., ultraviolet or infrared wavelength range. Light from light source 40 is irradiated onto glass sheet G by subsystem 16. In one example, the light source is selected to have a tuned, narrow band of wavelength λ1 through which glass sheet G is opaque or generally non-transparent. Light source 40 is also selected such that the wavelength λ1 of the light source stimulates or emits light at the surface of glass sheet G at a wavelength λ2 different from the light source. For example, light source 40 is selected such that the wavelength λ1 of the light source causes the surface of glass sheet G to fluoresce or glow at a wavelength λ2 that is longer than the wavelength λ1 of the light source. In a further example, laser 40 is a pulsed diode laser tuned to emit ultraviolet light at a particular wavelength where glass sheet G is opaque or non-transmissive, or where glass sheet G is substantially non-transmissive, e.g., with a transmission of less than 5% or less than 2% relative to the laser output, and the glass sheet fluoresces in the visible spectrum.

[0016] The subsystem 16 may also include various optical elements 42 for controlling and directing light from the light source to the glass sheet G and from the glass sheet G to the detector. The optical elements 42 may be configured to provide a planar laser sheet to one 44 of two surfaces 44, 46 of the glass sheet G. The planar laser sheet may extend across the conveyor, for example, in the X direction. The first and second surfaces 44, 46 are spaced apart by the thickness of the glass sheet G. Because the glass sheet G is opaque or substantially non-transparent to the laser sheet's wavelength λ1, the laser sheet intersects the first surface 44 without penetrating the glass sheet G or reaching the second surface 46, thus exciting the glass sheet G only at the first surface 44, and visible light of wavelength λ2 appears on the surface 44. This emitted light line is detected by the camera(s) 30 for the system 10.

[0017] The camera 30 can include a charge-coupled device (CCD) image sensor or a complementary metal-oxide semiconductor (CMOS) image sensor. In this embodiment, the detector 30 includes a CMOS sensor and is positioned so that the glass sheet G, i.e., the entire width of the glass sheet in the x-direction, is captured in an image. In the illustrated embodiment, the camera is a 5496x3672 pixel CMOS sensor camera set to a target area of 5496x1836 or 5496x1000 pixels in one embodiment, or a 5120x5120 pixel CMOS sensor in another embodiment. Various camera settings may be controlled based on laser parameters, conveyor speed, and other system factors. These camera settings include lens focal length, aperture, gain, and exposure time. In one example, the camera uses a fixed lens, such as a 16mm or 25mm lens, set to an aperture of f / 2.4 or greater to provide a large depth of field, and has an exposure time of 15-20 milliseconds with a gain of 2-15 dB. In alternative embodiments, the camera settings may use alternative exposure times, such as exposure times ranging from 10 milliseconds to 300 milliseconds or more, and the gain may similarly be set to alternative values ranging from 2 to 30 decibels. In other embodiments, the camera 30 may be positioned to image only selected areas of the sheet G, and in further embodiments, the detector may be provided as a separate photodetector or photosensitive element. In further embodiments, additional optical elements, such as filters, may be provided between the glass sheet G and the detector 30 to further enhance the signal-to-noise ratio.

[0018] Subsystem 16 has at least one computer and / or control unit 18 containing at least one processor program executing logic for controlling the optical system, including the detectors and any light sources, acquiring data from the detectors for each glass sheet, analyzing the data for the glass sheet, and acquiring information related to the glass sheet's surface shape, light distortion due to reflections, or other surface information or defects. The computer may be integrated with a control system 20 of inspection system 10, as shown, or may be provided as a separate device in communication with control system 20. Control system 20 may include a programmable control unit, or computer, for detecting the glass sheets advancing on the conveyor and for controlling the movement and speed of conveyor 12.

[0019] Thus, the optical subsystem 16 implements a non-contact inspection system that rapidly acquires detailed data corresponding to the surface of the glass sheet G as it is transported on the conveyor 12, for example, during or after bending, cooling, or other processing operations, with sufficient time to scan and analyze the glass sheet G or measure or gauge the glass sheet G or its surface, and analyzes the acquired surface data to evaluate and report characteristics related to the surface shape of the glass sheet G and the optical properties of the glass sheet G.

[0020] Conveyor 12 moves fixture 14, with or without glass sheet G, along a path, or direction shown here as the Y direction, past optical system 16. Conveyor 12 is moved using one or more motors and support rollers or other devices.

[0021] Inspection system 10 has one or more position sensors 22 for determining the position and timing of conveyor 12 for use in analyzing glass sheet G using subsystem 16 and for calibrating subsystem 16 using fixture 14. Position sensor 22 may comprise a digital encoder, an optical encoder, or the like. Position sensor 22 may be used as an input to optical system 16 to determine the timing of data acquisition, for example, as a camera trigger.

[0022] The inspection system 10 may include sensors, such as photoelectric sensors, in communication with the control systems 18, 20 to determine when the fixture 14 or glass sheet G is in the proper position on the conveyor 12 or has advanced to the subsystem 16. The computers 18, 20 then communicate with the subsystem 16 to activate the system 10 and begin measuring the surface of the sheet G. In other examples, the optical system 16 may operate continuously and begin acquiring and processing data related to the glass sheet G in response to a detector in the system 10 recognizing an appropriate signal indicating the beginning of an intersection between the light source and the glass sheet G.

[0023] In use, the system 10 can measure or gauge the glass sheet G using the light source 40 and the camera 30. The system 10 can scan and image the glass sheet G to create a three-dimensional map or point cloud of the surface of the glass sheet G.

[0024] To measure or gauge the glass sheet G, the computer 18 receives image data from the cameras 30 as a series of data representing a series of visible wavelength lines measured or detected using one or more cameras, each imaging a predetermined area of the glass sheet G. Each visible wavelength line is processed and analyzed to determine first and second coordinates, e.g., (x, y) coordinates, relative to the surface of the glass sheet in the series of coordinates associated with each line, which are stored in a matrix or point cloud associated with the cameras. A third coordinate, e.g., a (z) coordinate, is calculated by the computer 18 from the laser position, the camera position, and the first and second coordinates using triangulation, and the (z) coordinate is stored in the matrix or point cloud.

[0025] The computer 18 forms a matrix or point cloud of data from the image, e.g., cells in a matrix associated with positions on the surface 44 of the glass sheet, or an array of points in a point cloud associated with positions on the surface 44 of the glass sheet. A three-dimensional map of the surface of the glass sheet can then be created from the matrix or point cloud as a function of a set of coordinates for each of a set of visible wavelength lines for the imaged glass sheet G. Because the laser light does not penetrate the glass sheet G, only the surface 44 facing the inspection system is illuminated. In this manner, the point cloud with its set of coordinates constitutes a three-dimensional, high-resolution mathematical model of the surface 44 of the glass sheet G by a set of (x, y, z) coordinates.

[0026] Before measuring or gauging glass sheet G to create a point cloud or map of surface 44, system 10 may need to be calibrated to link the point cloud to a known coordinate system. This disclosure relates to fixtures and methods for performing such a calibration on system 10.

[0027] 2 shows a flowchart of a method 100 for calibrating an optical inspection system according to one embodiment. Method 100 may have steps rearranged, omitted, or additional steps added according to various embodiments.

[0028] Step 102 is a step of internally calibrating the subsystems 16, for example, the cameras, the light sources, and the conveyor 12, respectively.

[0029] The system 10 is externally calibrated via one or more steps associated with 104 .

[0030] At step 106, a fixture is provided for use with system 10. An example of fixture 200 is shown in FIG. 3 without glass sheet G and in FIG. 4 with glass sheet G. Another example of fixture 300 is shown in FIG. 7 without glass sheet G and in FIG. 8 with glass sheet G. Fixture 200, 300, or 400 may be provided as fixture 14 of FIG. 1. Each fixture is described in more detail below.

[0031] 3 and 4, fixture 200 includes a base frame 202 that is supported on the system conveyor and can be used to lift or move the fixture. Frame 202 includes a fixture frame 204. In the illustrated example, the fixture frame includes sidewalls 206 that extend upward from the frame to a top surface 208. The sidewalls may be shaped substantially similar to the perimeter of a glass sheet G intended for use with the fixture. The top surface 208 of the sidewalls may be contoured or otherwise shaped to fit the surface of the bottom surface 46 of the glass sheet G. The sidewalls may extend continuously through a central opening 210.

[0032] A series of standoff pins 220 extend upward from the upper surface 208. The series of standoff pins are spaced apart about the upper surfaces of the sidewalls. The standoff pins are provided to support the glass sheet in contact with the fixture. The series of standoff pins can define a datum A for the fixture. When the sheet G is supported in the fixture, the lower surface 46 of the sheet is spaced from the upper surfaces 208 of the sidewalls so that the lower surface of the sheet does not contact the upper surface of the fixture, and is supported only by the standoff pins.

[0033] The exact shape, size, surface shape, and contour of the actual glass sheet G may differ from the glass sheet defined in the CAD or other mathematical model. Therefore, given the variability of the glass sheet G, the actual glass sheet G may not contact every single standoff pin 220. A fixture with more than two standoff pins may overly constrain the system and fixture because the actual glass sheet G may deviate from the mathematically or CAD-modeled glass sheet. As shown, more than two standoff pins may be required to fully support the glass sheet in the fixture. In the illustrated example, there are 12 standoff pins, but more or fewer are also contemplated. In this scenario, the measurement data of the glass sheet G acquired by subsystem 16 may not be used to directly align the subsystem 16 point cloud of the surface of the glass sheet G to the CAD data because the necessary assumption that all of the standoff pins 220 are in contact with the glass sheet G may introduce errors into the alignment of the glass sheet.

[0034] The fixture 200 may also include additional datums for positioning the edges of the sheet G relative to the fixture. In the illustrated example, the fixture has a pair of datum B posts 230 and associated datum B mechanisms 232 for contacting the edges of the glass sheet G with the datum B posts. The B datum posts can position the edge of the sheet G relative to the fixture's X axis. The datum B mechanism may include a pneumatic or otherwise operated cylinder 234 and arm 236. The arm 236 contacts the edge of the sheet opposite the B datum post and translates the sheet G along the x axis until the sheet contacts the B datum post. In other examples, there is only one B datum post.

[0035] In the illustrated example, the fixture also includes a datum C-post 240 and an associated datum C-mechanism 242 for contacting the edge of the glass sheet G with the datum C-post. The C-datum post can position the edge of the sheet G relative to the Y-axis of the fixture. The datum C-mechanism includes a pneumatic or otherwise operated cylinder 244 and an arm 246. The arm 246 contacts the edge of the sheet opposite the datum C-post and translates the sheet G along the y-axis until the sheet contacts the datum C-post. In other examples, there may be two datum C-posts.

[0036] Although the standoffs 220 and B and C datum posts 230, 240 allow the glass sheet G to be precisely positioned relative to the fixture 200, when the glass sheet G is imaged in the system 10, the subsystem 16 may not be able to accurately and precisely define or locate the edge or boundary of the glass sheet. For example, errors and artifact points caused by the light source 40 intersecting the surface 44 and edge of the sheet G may cause errors in the edge measurement or the exact location of the edge in the point cloud of the glass sheet G. An example of an edge effect or measurement location bias is caused by the steering effect of the laser beam and / or a deviation in the calculated line center of the fluorescent line from the laser sheet to the surface of the sheet G. These effects and biases can create artifact points in the three-dimensional point cloud and lead to errors in locating the edge of the sheet using the system 10. Because this is a non-contact inspection system 10 and the distinct edges of the sheet G may not be possible or difficult to accurately and precisely define using three-dimensional point cloud data, it is still important to calibrate and align the fixture to provide a relative coordinate system for the system 10. In this manner, fixture 200 is aligned and calibrated using system 10 to compare the surface data of the system sheet G in the three-dimensional point cloud with a mathematical or CAD model to measure or gage the sheet, or to compare alignment data of fixture 200 with a CMM coordinate system and a CAD model to verify fixture alignment and coordinates, and / or to measure or gage the sheet.

[0037] Accordingly, the fixture 200 includes an optical fiducial 250, such as a checkerboard chart or other known, planar calibration surface 250. In the illustrated example, the optical fiducial 250 is provided as a calibration surface within an opening 210 surrounded by the sidewall of the fixture. The calibration surface may be located at the bottom of the upper surface of the sidewall so that the calibration surface can be present on the fixture regardless of the presence of a glass sheet G. The calibration surface may be positioned to be close to the height of an adjacent glass sheet G. The optical fiducial 250 is positioned relative to the upper surface of the sidewall so that the sidewall does not obstruct any portion of the optical fiducial from the field of view of the associated camera. In another example, the optical fiducial may be removable from the fixture and placed on the fixture only for alignment and calibration purposes, but not while the system 10 is imaging the glass sheet G. In another example, the optical fiducial may be covered for protection while the system 10 is measuring the glass sheet G.

[0038] In one example, the optical reference or calibration surface 250 is composed of a checkerboard of squares of a known number and size. The calibration surface may be connected to the fixture at a known position and angle, or may be generally located within the fixture, with the relationship between the checkerboard and the fixture's coordinates being determined later. In the illustrated example, the calibration surface 250 is located at the center of the fixture and is formed as a plane or flat surface. While the calibration surface 250 is planar, the calibration surface may also be tilted or at an angle relative to the fixture and / or the camera's viewing angle.

[0039] The optical fiducials 250 may include visual markers 252 or indicators to enable recognition of the fixture by the system 10. For example, the visual indicators may be bar codes, such as two-dimensional or three-dimensional bar codes, or other visual indicators or labels.

[0040] Optical fiducial 250 may also have three or more physical fiducials 270 , such as fiducial markers for relating the position and alignment of optical fiducial 250 to physical fiducials 260 of fixture 200 .

[0041] In one example, the entire optical fiducial 250, e.g., a checkerboard, is positioned so that it is visible to all cameras 30 or detectors in a system having more than one camera. In another example, in a system 10 having multiple cameras and multiple optical fiducials 250, each optical fiducial can be positioned to be within the entire field of view of its associated camera, and the system applies additional transformations to stitch or otherwise cross-reference the multiple camera data when creating calibrations and fixture alignments.

[0042] Fixture 200 may be provided with physical fiducials 260, such as tooling balls 260 or other CMM surfaces such as edges or openings. The physical fiducials 260 can be used to correlate CMM coordinates and data with system calibration and alignment data from optical fiducials 250 and fixture 200. In the illustrated example, fixture 200 includes three or more physical fiducials 260. The fixture may also have physical fiducials 270 on the calibration surface, such as physical fiducial markers, that can correlate the position and alignment of optical fiducials 250 with the rest of the fixture in a CMM coordinate system determined from the physical fiducials 260. Because system 16 uses non-contact optical inspection techniques and does not touch or physically engage the fixture, the position of a fixture in system 10 cannot be determined solely through the use of physical fiducials 260, such as tooling balls and / or CMM surfaces, or the CMM.

[0043] The physical fiducials 260 or other fixture CMM surfaces are spaced apart from one another on the fixture. The fixture location and fixture coordinate system can be transformed to a computer-aided design (CAD) or other model coordinate system using a coordinate measuring machine (CMM). In various embodiments, the CAD coordinate system may correspond to or relate to another coordinate system for use with the glass sheet G, such as a vehicle coordinate system or other final assembly coordinate system. To measure or calibrate the fixture, the CMM device moves to and physically contacts the tooling balls or other alignment surfaces of the fixture. The CMM device determines the position of the tooling balls on the fixture to provide three known coordinates of the fixture in the CMM coordinate system (e.g., three known points in a Cartesian or other CMM coordinate system). Conventional systems and gauging require contacting the surface of the glass sheet G with dozens or hundreds of probes to determine points relative to the sheet and measure or gauge the sheet surface.

[0044] 7-8, another fixture 300 is illustrated in accordance with another embodiment and may be used as fixture 14 in the system of FIG. 1 and / or as fixture 14 in the method of FIG. 2. For simplicity, components of fixture 300 that are the same as or similar to those shown and described above with reference to fixture 200 have been given the same reference numerals.

[0045] The fixture 300 has a base frame 202 that is supported on the system's conveyor and can be used to lift or move the fixture on a fixture frame 204. In the illustrated example, the fixture frame includes sidewalls 206 that extend upwardly from the frame to a top surface 308. The sidewalls 206 may be shaped substantially similar to the perimeter of a glass sheet G intended for use with the fixture, or may extend continuously as shown.

[0046] The fixture frame's top surface 308 is contoured or otherwise shaped to correspond to or match the top surface of the glass sheet G as defined by the model or CAD data for the glass sheet G. The top surface 308 may be configured as a continuous, full surface or a solid surface, and is surrounded by the sidewalls 206. In one example, the top surface 308 is machined to a shape based on the CAD data for the glass sheet G. In a further example, the top surface 308 is machined or otherwise formed to a shape that corresponds substantially to the center of tolerance of the CAD data for the glass sheet G. In one embodiment, the top surface 308 may be formed from or include a composite material. The top surface 308 may be measured by both the system 10 and the CMM device, and thus may serve as both an optical fiducial and a physical fiducial for the fixture 300.

[0047] When the fixture 300 is used with a curved glass sheet G, the first surface 44 of the glass sheet G has a different radius of curvature than the second surface 46 of the glass sheet G. In the illustrated non-limiting example, the first surface 44 has a larger radius of curvature than the second surface 46 of the glass sheet G. The top surface 308 of the fixture 300 has the same radius of curvature as the CAD model of the glass sheet G and can represent the ideal or model first surface 44 of the glass sheet G. FIG. 8 shows a schematic cross-sectional view of the fixture 300 with the glass sheet G.

[0048] A series of standoff pins 220 are provided in the fixture 300 to support the glass sheet G on the fixture's top surface 308. The standoff pins 220 extend upward from the top surface 308 and are spaced apart from one another about the periphery of the top surface 308. The standoff pins 220 space the glass sheet G from the fixture's top surface 308 and prevent the second surface 46 of the glass sheet from contacting the fixture. Because the second surface 46 of the glass sheet G has a different radius of curvature compared to the fixture's top surface 308, the standoff pins 220 have different heights, and the height of each standoff pin is determined using CAD data for the glass sheet G, along with data related to the shape of the top and bottom surfaces of the glass sheet G and the shape of the fixture's top surface 308.

[0049] It should be noted that the exact shape, size, and surface contour and profile of the actual glass sheet G may differ from the CAD or other mathematical model of the glass sheet G, and therefore, based on variations in the glass sheet G when placed on the fixture 300, the actual glass sheet G may not contact every single one of the standoff pins 220. The standoff pins 220 may function as datum A for positioning the glass sheet G relative to the fixture 300.

[0050] The fixture 300 may further include a datum for positioning an edge of the sheet G relative to the fixture. In the illustrated example, the fixture 300 includes one or more datum B posts 230 and associated datum B features 232, and one or more datum C posts 240 and associated datum C features 242.

[0051] In some embodiments, the top surface 308 of the fixture 300 may be formed from a material that fluoresces in response to light from a light source within the system 10, or the top surface 308 may have a coating that fluoresces in response to light from a light source within the system 10.

[0052] In some embodiments, the top surface 308 of the fixture 300 can include one or more optical fiducials 350. The optical fiducials 350 can be used to compare a three-dimensional point cloud representing the surface data of the sheet G to a mathematical or CAD model for measuring or gauging the sheet G, or to compare alignment data of the fixture 300 to a CMM coordinate system and a CAD model to verify the alignment and coordinates of the fixture and / or measure or gage the sheet. The fixture 300 can include one or more optical fiducials 350 for each detector or camera in the system 10. In further embodiments, the optical fiducials 350 can be located in areas of the top surface 308 that have a larger radius of curvature, e.g., flatter areas.

[0053] Each optical fiducial may be configured as a shape or marking on the fixture's top surface 308. In one example, the optical fiducials 350 may be configured as triangles, diamonds, etc., and may be defined by grooves machined into or protrusions extending outward from the surface 308. Thus, the optical fiducials 350 are detectable by the CMM machine so that they can be referenced to other datums in the fixture 300. Furthermore, because the optical fiducials 350 are formed on the fixture's surface 308, the position of the optical fiducials 350 relative to the fixture's surface 308 is also known. The optical fiducials 350 are also detectable by the system 10 because they cause a change in fluorescence that is detectable by the camera(s); for example, the optical fiducials 350 may cause a higher or lower intensity of fluorescent light relative to an adjacent surface 308 imaged by the camera. In another embodiment, a coating or other optical fiducial 350 may be used.

[0054] In one example, each camera has its own optical fiducial 350. In another example, the optical fiducial 350 may be large enough to extend across the fields of view of multiple cameras. In one example, for a system with more than one camera, at least a portion of the optical fiducial 350 is positioned so that it is visible to all cameras 30 or detectors in the system. In another example, for a system 10 with multiple cameras and multiple optical fiducials 350, each optical fiducial may be positioned to be entirely within the field of view of its associated camera, and the system applies an additional transformation based on the known positioning of the fiducials relative to each other to cross-reference multiple camera data together when creating calibrations and fixture alignments.

[0055] In some embodiments, the jig 300 may additionally include physical fiducials similar to those described above with reference to FIG. 3, such as tooling balls, or other CMM surfaces such as edges or openings.

[0056] Referring to Figure 9, in another embodiment, a fixture 400 is shown for use with the system of Figure 1 and the method of Figure 2. For simplicity, components of fixture 400 that are the same as or similar to those shown and described above with reference to fixture 200 have been given the same reference numerals.

[0057] The fixture 400 includes a base frame 202 and a fixture frame 204. In the illustrated example, the fixture frame has sidewalls 206 extending upwardly from the frame to a top surface 208. The sidewalls may extend continuously about a central opening 210. A series of standoff pins 220 extending upwardly from the top surface 208 are provided for contacting and supporting the glass sheet on the fixture. The series of standoff pins may define a datum A for the fixture.

[0058] An exemplary glass sheet G0 is provided with a fixture and supported on standoff pins 220. A first surface 44 of the glass sheet G0 can be used as a calibration surface in the system 10 of FIG. 1 and / or the method of FIG. 2. The glass sheet G0 can be removed after the calibration process or method 100, and the glass sheet G can be provided on the fixture 400 for measurement, gauging, etc. by the system 10. The first surface of the glass sheet G0 can serve as both a physical reference and an optical reference for the fixture 300, as it can be measured by both the CMM device and the system 10. In a further example, the glass sheet G0 can have optical fiducials etched or otherwise formed thereon, such as the optical fiducials 350 described above with respect to FIGS. 7-8, in addition to the optical fiducials provided by the first surface 44 of the glass sheet G0 itself.

[0059] In further embodiments, fixtures with fiducials, such as fiducials 250 and / or 350, may be provided for use with an exemplary glass sheet G0 by combining, for example, features of fixtures 200, 300 as described with respect to FIGS. 7-8 with fixture 400 as described with respect to FIG. 9 . For clarity, fiducials 250, 350 may also be referred to as camera optical fiducials, in this example, to distinguish them from the optical fiducials provided by the first surface 44 of the glass sheet G0 itself. For systems 10 with one or more cameras 30, optical fiducials 250, 350 may be provided for each camera 30 such that there is at least one fiducial 250, 350 for each camera 30. When used with glass sheet G0, optical fiducials have additional features for alignment algorithms to reference, which may provide a faster, more accurate, and / or more precise overall solution.

[0060] The fixture 400 may also include additional datums, and in the example shown, the fixture includes a pair of datum B posts 230, associated datum B features 232, a datum C post 240, and associated datum C features 242.

[0061] The fixture may further be provided with physical references 260, such as tooling balls 260, or other CMM surfaces such as edges, openings, etc. The glass sheet G0 is positioned relative to known tooling ball locations on the fixture using datums and standoff pins on the fixture 400.

[0062] 2, steps 106-114 illustrate some of the sub-methods 104 for validating fixtures 200, 300, 400 or for correlating, relating, and transforming between fixture coordinates, calibration surface coordinates, CMM coordinates, and CAD coordinates. For simplicity, fixture 14 will be used generically below with respect to the method steps, and reference may be made to the use of any of fixtures 200, 300, 400. Additionally, steps described for use with one of fixtures 200, 300, 400 and system 10 may also be applied to the other fixtures disclosed herein.

[0063] When the fixture 14 is provided in step 106, the mathematical model of the glass sheet G may be provided in a model or CAD coordinate system. In the case of the fixture 200, the location of the fixture tooling ball 260 may also be provided in a CAD coordinate system, for example, as a fixture tooling ball coordinate system. A relationship between the CAD coordinate system and the fixture tooling ball coordinate system is determined.

[0064] For fixtures 300 and 400, the mathematical model of glass sheet G receptively includes and corresponds to the fixture's top surface 308 or the top surface of glass sheet G. In a further embodiment, a mathematical model or file can be generated that includes the mathematical model of top surface 308 or the top surface of sheet G in CAD coordinates, as well as any tooling ball locations and glass datums on the fixture.

[0065] In step 108, fixture 14 can be calibrated using a CMM machine. In the case of fixture 200, the CMM machine has a CMM coordinate system. The CMM machine measures physical fiducials 260 of the fixture and / or other CMM surfaces on the fixture. The CMM machine also measures any physical fiducials 270 on the optical fiducials. The CMM machine provides an optical fiducial CMM surface coordinate system. The CMM machine can also provide a fixture CMM coordinate system. Both the optical fiducial CMM surface coordinate system and the fixture CMM coordinate system are referenced to a CMM coordinate system, as described below with reference to the example of FIGS. 6A-D. Fixture 200 can be measured using the CMM machine to determine the positions in CMM coordinates of the fixture's first and second sets of physical and optical fiducials.

[0066] The fixture 300 can be measured using a CMM machine to confirm that the shape of its top surface 308 corresponds to the first surface 44 of the glass sheet G in the CAD data. The CAD data can be positioned relative to datums and fiducials on the fixture 300 that are known in the measured CMM data. Data including both the CAD data, the calibration surface 308, the optical fiducials 350, and other datum positions relative to the CMM coordinate system can be generated, for example, as a file. This can enable a unified coordinate system between the CAD coordinate system and the CMM coordinate system. In other examples, the top surface 308 of the fixture 300 is not measured using a CMM machine, and step 108 can be omitted.

[0067] For jig 400, glass sheet G0 is measured using a CMM machine to determine the shape of sheet G0 and to reference sheet G0 to any tooling balls in jig 400. Data may be generated, for example as a file, including first surface 44 of sheet G0, any optical fiducials on sheet G0, and other datum locations relative to the CMM coordinate system.

[0068] At step 110, fixture 14 is placed in system 10. The fixture is placed in a known position on fixture conveyor 12, and the fixture is imaged using camera 30 or other detector in system 10. Fixture 14 can be imaged without operation of system light source 40, for example, if the light source is a laser and fixture 200 is present. Alternatively, fixture 14 can be imaged while light source 40 is activated, such as when fixture 300 or 400 is in use.

[0069] The fixture 200 can be positioned in the system 10 without the glass sheet G at the height that the fixture 200 would be positioned in the system with the glass sheet G.

[0070] The fixture 300 may be placed in the system 10 without a glass sheet G and may be elevated within the system 10 so that the top surface 308 is located at a height corresponding to the top surface of the glass sheet G when it is on the fixture 300 within the system 10. This places the fixture surface 308 at the same height or Z position as the top surface of the glass sheet G when it is measured on the system 10. It should be noted, therefore, that the height or position of the top surface 308 will be different between the calibration method and when the sheet G is being inspected, measured, or gauged.

[0071] Fixture 400 may be placed into the system with exemplary sheet G0 at the height at which fixture 200 would be placed in the system with sheet G to be measured or tested. Note that sheet G0 is removed and replaced with sheet G for the inspection, measurement, or gauging process. Sheet G0 may be stored for later use, such as for recalibrating fixture 400.

[0072] In the case of a fixture that combines the use of optical standards 250, 350 and exemplary glass sheet G0, as described above, the fixture can be placed in the system without glass sheet G0 to perform a first measurement and test, and then placed in the system with glass sheet G0 to perform a second measurement and test, or vice versa.

[0073] 5A is a schematic diagram of a fixture 14 with one camera 30, or two cameras 30, positioned on either side of the fixture, e.g., upstream and downstream of the fixture. The fixture can be positioned within the system, as described above, so that the optical fiducials are fully within the field of view of all camera(s). Use of fixture 200 is not limited to FIG. 5A.

[0074] FIG. 5B shows a schematic diagram of fixture 14 with two cameras located on the same side of the fixture, e.g., both upstream or both downstream. The fixture can be positioned within the system such that the optical fiducials are fully within the field of view of both cameras, as described above. The use of fixture 200 is not limited to FIG. 5B.

[0075] 5C shows a schematic diagram of a fixture 14 with multiple optical fiducials 350 and multiple cameras 30, where each camera has at least one of the optical fiducials completely within its field of view and the positions of the optical fiducials relative to one another are known. Use of fixture 300 is not limited to FIG. 5C.

[0076] 2, in step 112, the fixture and optical fiducials are imaged using detector 30 in system 10. System 10 then creates an optical reference coordinate system and further creates an optical reference CMM surface coordinate system.

[0077] In the case of fixture 200, optical fiducial(s) 250 are imaged using camera 30 to provide an optical calibration of the fixture without glass sheet G and to position the optical fiducials in the system 10 coordinate system, e.g., as a reference coordinate system, as measured and referenced to the optical data and camera. The optical fiducials can be positioned or optically calibrated just once, or they can be positioned and optically calibrated each time they are positioned on the conveyor.

[0078] The image data may be processed to reduce noise, for example, by applying a threshold to the image, normalizing the image, transforming the image using a Fast Fourier Transform, filtering the image, etc.

[0079] The computer system creates an optical reference coordinate system based on the optical data calibration plane. The size or other characteristics of the checkerboard squares on the optical fiducial 250 are known for calibration in the x and y directions. Calibration in the z direction precisely identifies the positions of the optical fiducial and fixture in the image based on the relationship between the x and y calibrations, creating an optical coordinate system. Details of creating an optical coordinate system from an image are described below with reference to the examples shown in Figures 6A-C.

[0080] According to one embodiment, a checkerboard or other optical fiducial 250 can be applied to a substrate on a fixture, such as as a decal. In other examples, the checkerboard can be printed directly on the substrate, the optical fiducial 250 can be formed on the substrate, or the optical fiducial 250 can be provided in other ways. Depending on how the optical fiducial is applied to the substrate, the position of the optical fiducial or checkerboard on the substrate itself may vary, so the position of the optical fiducial 250 relative to the fixture must be determined. Therefore, the optical fiducial 250 also has an associated physical fiducial 270. The physical fiducial 270 can be formed before or after the optical fiducial 250 is installed in the fixture. Imaging the optical fiducial 250 in step 112 also includes imaging the physical fiducial 270. For image analysis, the physical fiducial 270 is positioned in the optical fiducial CMM surface coordinate system, and similarly, the optical fiducial 250 is positioned in the optical fiducial coordinate system. Both coordinate systems are then referenced to image space. For image analysis, the location of the physical fiducial 270 or marker can be identified based on the visual characteristics of the physical fiducial 270.

[0081] For the fixture 300 and step 112, the fixture 300 may be imaged while the system light source 40 or laser is activated. The fixture's top surface 308 may be formed from a material that fluoresces in response to light from the laser, or the top surface 308 may be painted or coated to fluoresce in response to the light source. Each camera 30 may image its associated fiducial 350. Each camera 30 provides associated image data and a point cloud for an associated viewing area on the top surface 308. The system 10 performs an optical calibration of the fixture 300 without the glass sheet G and identifies the positions of the top surface 308 and the optical fiducials 350 in a coordinate system of the system 10, e.g., an optical reference coordinate system, that is measured and referenced to the optical data and cameras.

[0082] The fixture 400 may be imaged in step 112 while the system light sources 40 or lasers are activated. The top surface of Sheet G0 fluoresces in response to the light from the lasers, and each camera 30 provides associated image data and point clouds for the associated viewing area within the system 10. The system 10 performs an optical calibration of the fixture 400 using the optical data and the exemplary Sheet G0 in the system 10 coordinate system measured and referenced to the cameras, for example, as an optical reference coordinate system.

[0083] In the case of a fixture using a combination of optical fiducials 250, 350 and an exemplary glass sheet G0 to perform calibration, the optical fiducial(s) 250, 350 can be imaged as described above to perform optical calibration of the fixture without the glass sheet present, and the optical fiducials can be located in the optical reference coordinate system of system 10 in a first data set, which can include image data from a single camera or data stitched from multiple cameras using appropriate transformations. The exemplary glass sheet G0 is placed on the fixture, and the fixture is imaged as described above with respect to the exemplary glass sheet G0, and in a second data set, optical calibration of sheet G0 in the optical reference coordinate system of system 10 is performed. Image data from the optical fiducials, such as fiducials 250, 350, can be used to define transformations to align and combine data from multiple cameras together in the optical reference coordinate system of system 10. Image data from the surface of the exemplary glass sheet G0 can be used in defining transformation(s) to correlate the optical reference coordinate system of system 10 to a CAD coordinate system, as described below, for example, by correlating the optical coordinate system to CMM data and coordinate systems. In step 114, the optical reference coordinate system can be correlated to the CMM coordinates and / or the optical reference CMM coordinate system. As described below with reference to the example of Figures 6A-D, a linear algebraic transformation can be applied that results in transformation matrices relating the CMM-determined optical reference coordinates to the optically determined optical reference coordinates and the CAD coordinate system.

[0084] In step 130, the system 10 is ready to begin measuring or gauging the surface, i.e., inspecting the glass sheet G on the fixture, by comparing the point cloud matrix defining the surface with CAD data that represents what the surface of the sheet G should look like. The glass sheet G is scanned using subsystem 16 to create a point cloud or matrix of the glass sheet surface. The system uses a calibration and transformation matrix between the optically determined optical reference coordinate system and the CAD coordinate system to position the point cloud of the sheet surface relative to the CAD data within the CAD coordinate system. The CMM data and coordinates, any data from probes, standoffs, sheet G surface cloud, etc., and the known position of the fixture in the CAD coordinate system allow for a correlation or transformation from the optically determined coordinates to CAD coordinates. These transformations allow for comparison between different data from different coordinate systems and measurement systems.

[0085] Once the fixture has been verified with the CMM machine, the fixture calibration process can proceed and step 108 can be omitted since the transformation or correlation between the optical coordinates and the CMM coordinates is already known.

[0086] In a further example, the calibration process and method 100 omits step 108 and the use of CMM data and coordinates, and directly performs the conversion or correlation between optical coordinates and CMM coordinates based on optical fiducials being built into the fixture at known, precise, and accurate locations.

[0087] 6A-6D illustrate various methods for correlating optical coordinates, CMM coordinates, and CAD coordinates. The methods may be implemented in whole or in part by the control systems 18 and 20 of the system 10. Alternatively, portions of the methods may be implemented by another system, such as a CMM, with transformations to the CMM coordinate system and CAD coordinates entered into a memory connected to the control systems 18 and 20 of the system 10. The methods illustrated in FIGS. 6A-D may be implemented in other forms involving other transformations between various coordinate systems based on available data and systems, and the examples illustrated in FIGS. 6A-D are intended to illustrate methods for correlating coordinate systems for use with the system 10. In one non-limiting example, the method illustrated in FIGS. 6A-C may be used with tool 200, 300, or 400. In another non-limiting example, the method illustrated in FIGS. 6A, B, and D may be used with tool 300 or 400.

[0088] FIG. 6A illustrates, according to one non-limiting example, deriving a coordinate system from three non-linear points P1, P2, and P3. The three non-linear points may represent three different points measured in the CMM coordinate system using a CMM from a physical reference 260, such as a tooling ball on the fixture 14 or other CMM surface. To convert the three non-linear points to a three-dimensional coordinate system, such as a Cartesian coordinate system, the controller selects P1 as the origin. Next, the positive X-axis is defined as the unit vector from P1 to P2. The Y-axis is defined by the controller as a unit vector perpendicular to the previously defined X-axis and in the plane defined by P1, P2, and P3. Finally, the Z-axis is calculated by the controller as the cross product of the previously defined X-axis and Y-axis. In other examples, other conventions may be used by the controller to define the coordinate system from the three points, as long as the conventions are consistent, and other coordinate systems may also be used.

[0089] FIG. 6B illustrates deriving a coordinate system from an optical reference, such as a checkerboard, other calibration surface, or fixture surface, according to one non-limiting example. The coordinate system may be derived by the control system of system 10 as an optical coordinate system based on data from a detector or camera of system 10. In one non-limiting example, the origin is defined by the controller as one of the inside corners of the checkerboard, as shown in FIG. 6B. For a Cartesian coordinate system, the controller aligns the X axis along one edge of the checkerboard and the Y axis along the other edge, so that the checkerboard or optical reference lies in the XY plane. The Z axis is calculated by the controller as the cross product of the X and Y axes. In other examples, other conventions may be used by the controller to define the coordinate system from three points, as long as the conventions are consistent, and other coordinate systems may also be used.

[0090] 6C illustrates a schematic chain of transformations that may be used to convert between various coordinate systems for use in the system 10 and method 100 of the present disclosure. According to one example, the transformation between two given coordinate systems may be provided by a transformation matrix, an equation, etc., as calculated via linear algebra. The transformation between two coordinate systems may be constructed by a translation from the first coordinate system to the second coordinate system, a rotation from the first coordinate system to the second coordinate system, and / or a scaling of the first coordinate system relative to the second coordinate system, via a transformation matrix between the two respective coordinate systems.

[0091] According to this embodiment, system 10, fixtures 14, 200, 300, 400, and method 100 use five coordinate systems, although various other coordinate systems are possible based on the data available to system 10. These five coordinate systems are represented in Figure 6C, which schematically illustrates the transformations and transformation matrices between them. According to this embodiment, the five coordinate systems are as follows:

[0092] A CAD or model coordinate system may be provided to represent the glass sheet G in a product, end use, or other configuration.

[0093] A CMM coordinate system is provided and represents the default coordinate system used and measured by the CMM machine.

[0094] A physical reference coordinate system is provided, where the coordinate system of the physical reference 260 is represented by three points given in CAD coordinates, for example, the CAD model or the tooling ball of the fixture 200 modeled or positioned in space.

[0095] An optical reference coordinate system, e.g., a checkerboard coordinate system, is provided to represent the coordinate system of the optical reference 250 on the fixture, or the coordinate system of the calibration surface and optical reference 350 on the fixture, or the surface of the exemplary glass sheet G0, measured using the detector(s) or camera(s) of the system 10.

[0096] An optical reference CMM surface coordinate system is provided and may represent a coordinate system defined by three points represented by physical references 270 on the optical reference, such as by edges, openings, or other fiducial markers in the plane of the checkerboard, measured using the detector(s) or camera(s) of the system 10, or may represent the calibration surface and optical reference 350 on the fixture, or the surface of the exemplary glass sheet G0.

[0097] Transformations and transformation matrices may be provided as a non-limiting example between the above coordinate systems as follows:

[0098] A transformation T0 from the CAD system to the fixture's physical reference system can be defined, which in this example can be determined directly without any mathematical transformation since the tooling ball or other physical reference 260 is already defined in CAD coordinates.

[0099] A transformation T1 may be defined to transform the physical reference coordinate system into the CMM coordinate system by measuring the physical fiducials 260 of the tooling ball or other fixture in the CMM coordinate system via the CMM apparatus.

[0100] Transformation T2 is provided and derived using T0 and T1 to perform a transformation or transformation from the CAD coordinate system to the CMM coordinate system.

[0101] Transformation T3 may be performed to transform the optical reference coordinate system to the optical reference CMM surface coordinate system, for example, to relate the coordinate system of the checkerboard to the coordinate system of physical fiducials 270 on the checkerboard. In one example, transformation T3 only involves transformation in two dimensions, i.e., the XY plane of the optical reference or checkerboard, and therefore may be determined via measurements or data from a detector or camera of system 10. Determining the transformation may require absolute alignment of the optical references in the fixture with respect to the X and Y axes.

[0102] Transformation T4 may be defined as a transformation from the optical reference CMM surface coordinate system to the CMM system by measuring the physical reference 270 on the optical reference or CMM surface in CMM coordinates via the CMM apparatus.

[0103] To perform the transformation or transformation from the optical reference CMM surface coordinate system to the CAD coordinate system, a transformation T5 may be defined and derived using T2 and T4.

[0104] Finally, a transformation T6 can be defined and derived from T3 and T5 to perform a transformation or transformation from the optical reference coordinate system to the CAD coordinate system.

[0105] By relating the coordinate system of the calibration surface to the coordinate system of the CAD, the below-described point cloud or three-dimensional map of the surface of sheet G from the camera can be accurately and precisely positioned within the CAD model for measurement and gauging.

[0106] The computer 20 receives image data from the camera 30. The computer 20 uses the data from the images, such as cells in a matrix associated with locations on the surface 44 of the glass sheet, or an array of points in a point cloud associated with locations on the surface 44 of the glass sheet, to form a matrix or point cloud. The control system can perform various noise reduction steps as post-processing on the point cloud. The three-dimensional map of the surface of the glass sheet G determined from the point cloud is then registered or referenced by the system 10 relative to a calibration surface, or a coordinate system of the calibration surface and optical references. This allows a transformation matrix such as T6 to be used to convert the three-dimensional map of the surface of the glass sheet G to a CAD model, allowing the measured surface map to be compared to the CAD model, for use in, for example, measurement, gauging, or other inspection functions.

[0107] The CAD model may include a mathematical or dimensional model of the glass sheet G in a CAD coordinate system. The dimensional model may be provided using computer-aided design (CAD) models and / or data, or other mathematical models or representations of dimensions or shape. The control system may select the appropriate CAD model, dimensional model, and transformation based on identification of the fixture using a calibration surface or visual indicators on the fixture.

[0108] Figure 6D shows another schematic diagram of a chain of transformations that may be used to convert between various coordinate systems for use with the system 10 and method 100 of the present disclosure, which may be used in place of the transformation shown in Figure 6C. Although Figure 6D shows a system 10 having four detectors or cameras, Figure 6D may be modified for use with a system 10 having any number of detectors, such as one, or less than four, or more than four.

[0109] According to one example, a transformation between two given coordinate systems may be provided by a transformation matrix, equations, etc., as calculated via linear algebra. A transformation between two coordinate systems may consist of a translation from the first coordinate system to the second coordinate system, a rotation from the first coordinate system to the second coordinate system, and / or a scaling of the first coordinate system relative to the second coordinate system, via a transformation matrix between the two respective coordinate systems.

[0110] According to this embodiment, system 10, fixtures 14, 300, 400, and method 100 use two or three coordinate systems, although a variety of other coordinate systems are possible based on the data available to system 10. The CMM coordinate system and the optical reference coordinate system are represented, by way of non-limiting example, in FIG. 6D, which shows a schematic illustration of the transformations and transformation matrices between them.

[0111] Transformation T7 may be provided or derived to perform a conversion or transformation from the CAD coordinate system to the CMM surface coordinate system. In other examples, transformation T7 may be omitted. The calibration surfaces and optical fiducials of fixtures 300, 400 may be measured with the CMM machine so as to be directly referenced to the CMM surface coordinate system.

[0112] One or more transformations T8 may be defined to relate the optical reference coordinate system to the model coordinate system. A model of the glass sheet may be provided in the model coordinate system based on CMM data of the calibration surface 308 or sheet surface G0 and any other references measurable by the CMM system, or CAD data. In a further example, transformations T7 and T8 are used to relate the optical reference coordinate system to the model coordinate system.

[0113] One or more transformations T8 can transform the optical reference coordinate system to the CMM surface coordinate system, for example, to relate the coordinate system of the calibration surface and optical references to the coordinate system of the checkerboard physical reference 270. In one example, transformation T8 can be defined via measurements or data from detectors or cameras of system 10 and known positions of detector 30 and light source 40.

[0114] For example, the computer 20 can determine or calculate points along the model line based on visible and fluorescent image data on the calibration surface of the fixture. In this manner, the computer 20 calculates the points of the model line as a series of coordinates or (x, y) data sets. These (x, y) data sets are entered by the computer 20 into associated cells of a matrix or point cloud. Each data set can include (x, y) values corresponding to the position of the calibration surface in the xy plane.

[0115] A third coordinate, such as the (z) coordinate of the calibration surface, is triangulated using the laser position, the camera position, and the first and second coordinates and stored in a matrix or point cloud. The computer 20 can calculate a z value for each set of (x,y) coordinates associated with the z position of that coordinate set on the calibration surface. The computer enters the (z) values into the associated cells of the matrix with the corresponding (x,y) coordinates to complete a map of the calibration surface viewable to the camera 30. Methods for determining an (x,y,z) data set or point cloud from a surface using the system 10 are further described in PCT Patent Application Serial No. PCT / US19 / 43180 and can be used herein, according to one embodiment, to determine the (x,y,z) coordinates or data set of the calibration surface of a fixture.

[0116] Once the calibration surface point cloud is determined in the optical coordinate system by the system 10, the computer 20 associates the optically measured calibration surface data or calibration surface point cloud data with CMM data or CAD data for the calibration surface of the fixture. According to one example, the optically measured calibration surface data is aligned to the CMM data using a surface fitting algorithm to create a transformation T8. Optical fiducials on the calibration surface of the fixture may further assist in aligning and fitting the optically measured calibration surface data to the CMM data, especially in flat areas. The transformation T8 can translate and / or rotate the point cloud from each camera 30 to the associated CMM or CAD data for the same area of the sheet.

[0117] In a further example, if the CMM data is identical to the CAD data, a surface fitting algorithm can be used to directly align the optically measured calibration surface data to the CAD data; if not, a transformation T7 can be performed.

[0118] In the illustrated example, a separate transformation T8 is determined for each detector or camera 30, and these transformations are illustrated as T8a, T8b, T8c, and T8d. Transformations T8a-d may be maintained as separate transformations associated with different regions of the calibration surface and sheet. As such, they can be easily regenerated without needing to be correlated or combined with one another. According to one embodiment, separate transformation matrices T8a-d are used with system 10 when an invariant metric, such as optical reflectance, is determined by system 10 for sheet G on fixtures 300, 400. According to another embodiment, transformation matrices T8a-d may be combined into a single transformation matrix T8 for use with system 10 when system 10 is used for non-contact gauging of sheet G on fixtures 300, 400. Adjacent fields of view of cameras may overlap one another.

[0119] Transformation T8 can be easily reproduced using system 10 and fixtures 300, 400 for different positions of the fixture or seat in system 10, for example, at different tilt angles. Additionally, use of fixtures 300, 400 allows transformation T8 to be easily reproduced if components of system 10 are reconfigured, and also allows for drift or errors in system 10 over time to be accounted for.

[0120] With an optical reference coordinate system related to the CMM coordinate system and / or CAD coordinate system, the below-described point cloud or three-dimensional map of the surface of sheet G from the camera can be accurately and precisely positioned within the CAD model or other model for measurement and gauging using transformation matrices T8.

[0121] Once the sheet G is placed on the fixtures 300, 400 of the system 10, the computer 20 receives image data from each camera 30. The computer 20 uses the data from the images, for example, as cells in a matrix associated with positions on the surface 44 of the glass sheet, or as an array of points in a point cloud associated with positions on the surface 44 of the glass sheet, to form a matrix or point cloud. The control system can perform various noise reduction steps as post-processing on the point cloud. The three-dimensional map of the surface of the glass sheet G determined from the point cloud is then registered or referenced by the system 10 relative to the coordinate system of the calibration surface and optical fiducials. This allows the three-dimensional map of the surface of the glass sheet G to be transformed into a CAD or other model using a transformation matrix T8, or compared to CMM data, allowing the measured surface map to be compared to the CAD model and used, for example, for measurement, gauging, or other inspection functions.

[0122] The CAD model may have a mathematical or dimensional model of the glass sheet G in a CAD coordinate system. The calibration surface of the fixture 300, or the top surface of the exemplary sheet G, may be based on or referenced to this CAD model so that they correspond directly to one another or have a known relationship based on T7. The dimensional model may be provided using computer-aided design (CAD) models and / or data, or other mathematical models or representations of dimensions or shape. The control system may select the appropriate CMM or CAD model, dimensional model, and transformation based on fixture identification using one or more visual indicators on the fixture 300, 400.

[0123] Method 100 provides for locating and calibrating the surface of glass sheet G using non-contact gauging and comparing the resulting map of the sheet determined by the system to a CAD or other gauging model in another coordinate system. The fixture and associated calibration and inspection method enable accurate and precise in-progress monitoring and inspection of the part, allowing for quick and easy gauging of a series of different parts and the use of multiple dimensional models. Furthermore, non-contact gauging according to method 100 reduces the time and expense associated with gauging parts because dimensional models can be easily created, modified, or updated using CAD data and calibration transform updates, eliminating the need for precision measurement gauging tools for part-specific contact gauging.

[0124] In further embodiments, the fixture and method may be used with an optical system to calibrate a system for optically inspecting objects other than glass sheets G. As one non-limiting example, an optical system with a laser emitting light at another wavelength, such as a visible wavelength, can be used to scan an object having a scattering surface. The optical system uses one or more cameras in a manner similar to that described above to determine a three-dimensional surface map of the scattering surface.

[0125] Aspects of the disclosure

[0126] Aspect 1. An optical inspection system includes a fixture supporting a glass sheet, the fixture having optical fiducials disposed thereon. An ultraviolet laser and associated optics form a planar laser sheet directed at the glass sheet, the planar laser sheet intersecting the surface of the glass sheet causing the surface of the glass sheet to fluoresce and form visible wavelength lines on the surface. A camera has an image sensor for detecting the optical fiducials and detecting the visible wavelength lines across at least a portion of the width of the sheet. A control system is configured to (i) image the optical fiducials on the fixture, (ii) define an optical reference coordinate system from the imaged optical fiducials, (ii) receive a mathematical model of the glass sheet in a model coordinate system, and (iii) relate the optical reference coordinate system to the model coordinate system via at least one transformation.

[0127] Embodiment 2. The system of any preceding or subsequent embodiment, wherein the control system is further configured to: (i) receive image data indicative of a visible wavelength line from a camera; (ii) analyze the data from the camera to determine first and second coordinates in a set of coordinates associated with the line; (iii) triangulate a third coordinate associated with each of the first and second coordinates in the set of coordinates; and (iv) create a three-dimensional map of the surface of the glass sheet as a function of the set of coordinates.

[0128] Aspect 3. The system of any preceding or subsequent aspect, wherein the control system is further configured to transform the three-dimensional map via at least one transformation to associate the three-dimensional map with the model coordinate system.

[0129] Aspect 4. The system of any preceding or subsequent aspect, wherein the control system is further configured to output an indicator indicative of the measurement value of the glass sheet in response to comparing the three-dimensional map to the mathematical model in the model coordinate system.

[0130] Aspect 5. The system of any preceding or subsequent aspect, wherein the control system is further configured to determine the indicator as a simulated light reflectance of the surface using a three-dimensional map of the surface compared to a mathematical model in a model coordinate system.

[0131] Embodiment 6. The system of any preceding or subsequent embodiment, wherein the control system is further configured to determine the indicators for gauging the glass sheet using a three-dimensional map of the surface.

[0132]

[0013] Aspect 7. The system of any preceding or subsequent aspect, wherein the control system is further configured to receive a series of data from the camera indicating a series of visible wavelength lines measured across the width of the sheet, each line corresponding to a different location along the surface of the glass sheet. The control system is further configured to analyze each of the series of visible wavelength lines to determine first and second coordinates in a series of coordinates associated with each line, triangulate a third coordinate associated with each of the first and second coordinates in each of the series of coordinates, and create a three-dimensional map of the surface of the glass sheet from each of the series of coordinates.

[0133] Embodiment 8. The system of any preceding or subsequent embodiment, wherein the wavelength of the ultraviolet laser is selected to be non-transparent through the glass sheet.

[0134] Embodiment 9. The system of any preceding or subsequent embodiment, wherein the fixture has a first set of physical references, the first set of physical references having at least three coordinates in the model coordinate system.

[0135] Embodiment 10. The system of any preceding or subsequent embodiment, wherein the first set of physical references for the fixture is provided by a calibration surface having a shape corresponding to at least a portion of a surface of the glass sheet.

[0136] Embodiment 11. The system of any preceding or subsequent embodiment, wherein the calibration surface further forms an optical reference.

[0137] Embodiment 12. The system of any preceding or subsequent embodiment, wherein the fixture has at least one optical reference, the at least one optical reference being positioned on the calibration surface.

[0138] Embodiment 13. The system of any preceding or subsequent embodiment, wherein the at least one optical reference further provides at least one physical reference.

[0139] Aspect 14. The system of any preceding or subsequent aspect, wherein the control system is further configured to determine or derive a transformation from the optical reference coordinate system to the model coordinate system.

[0140] Embodiment 15. A system according to any preceding or subsequent embodiment, wherein the fixture has a calibration surface shaped to correspond to at least a portion of the surface of the glass sheet provided by exemplary glass sheet G0 to provide a first optical reference.

[0141] Aspect 16. The system of any preceding or subsequent aspect, wherein the fixture has camera optical fiducials associated with each camera.

[0142] Aspect 17. A system as described in any preceding or subsequent aspect, wherein the control system is further configured to image camera optical references to relate each camera to each other via at least one separate transformation, and to separately image a calibration surface as an optical reference to relate the optical reference coordinate system to the model coordinate system via at least one transformation.

[0143] Aspect 18. The system of any preceding or subsequent aspect, wherein the control system is configured to determine or receive a transformation relating a physical reference coordinate system of the fixture to the model coordinate system, the transformation being determined using a first set of physical references from the fixture.

[0144] Embodiment 19. The system of any preceding or subsequent embodiment, wherein the optical fiducials also define a second set of physical fiducials. The control system is configured to image the second set of physical fiducials and associate the second set of physical fiducials with the optical reference coordinate system.

[0145] Aspect 20. The system of any preceding or subsequent aspect, wherein the control system is configured to determine or receive a transformation relating a physical reference coordinate system of the fixture to a physical reference coordinate system of the optical reference, said transformation being determined using a first set of physical references from the fixture and a second set of physical references from the optical reference.

[0146] Embodiment 21. The system of any preceding or subsequent embodiment, wherein the control system is further configured to determine or receive a transformation relating the fixture's physical reference frame to a second set of physical references.

[0147] Embodiment 22. The system of any preceding or subsequent embodiment, wherein the control system is further configured to determine or derive a transformation from the model coordinate system to a second set of physical references.

[0148] Aspect 23. The system of any preceding or subsequent aspect, wherein the control system is further configured to determine or derive a transformation from the optical reference coordinate system to the model coordinate system.

[0149] Embodiment 24. The system of any preceding or subsequent embodiment, wherein the fixture has a series of standoffs for supporting the glass sheet, a first datum for positioning the glass sheet relative to the fixture, and a second datum for positioning the glass sheet relative to the fixture.

[0150] Aspect 25. A method of using a non-contact optical inspection system is provided. A fixture for supporting a glass sheet is provided, and the fixture is provided with optical fiducials. The optical fiducials on the fixture are imaged via a camera in the inspection assembly. An optical reference coordinate system is defined via a control system by analyzing the imaged optical fiducials. A mathematical model of the glass sheet in a model coordinate system is received via the control system. The optical reference coordinate system is related to the model coordinate system via at least one transformation via the control system.

[0151] Embodiment 26. The method of any preceding or subsequent embodiment, wherein a planar laser sheet is formed from an ultraviolet laser and associated optics of an inspection assembly and directed toward a surface of a glass sheet on a fixture. The surface of the glass sheet is excited at an intersection of the planar laser sheet and the surface, forming a visible wavelength line on the surface of the glass sheet. The visible wavelength line is imaged by a camera. By analyzing the imaged data from the camera, first and second coordinates of a set of coordinates associated with the visible wavelength line are determined. A third coordinate associated with each of the first and second coordinates of the set of coordinates associated with the visible wavelength line is determined by triangulation. A three-dimensional map of the surface of the glass sheet is created as a function of the set of coordinates.

[0152] Embodiment 27. The method of any preceding or subsequent embodiment, wherein the three-dimensional map is transformed via at least one transformation to relate the three-dimensional map to a model coordinate system. A constant index is calculated using the three-dimensional map in comparison to a mathematical model of the surface in the model coordinate system. The constant index is then output.

[0153] Aspect 28. The method of any preceding or subsequent aspect, wherein the at least one transformation is defined as at least one transformation matrix.

[0154] While exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms of the invention and / or disclosure. Rather, the words used herein are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the invention. Furthermore, features of various embodiments can be combined to form further embodiments of the invention.

Claims

1. 1. An optical inspection system comprising: a fixture supporting a glass sheet and having optical fiducials mounted thereon; an ultraviolet laser and associated optics that forms a planar laser sheet directed at the glass sheet, intersecting the planar laser sheet with the surface of the glass sheet to cause the surface of the glass sheet to fluoresce and form visible wavelength lines on the surface; a camera having an image sensor for detecting the optical fiducial and for detecting the visible wavelength line across at least a portion of the width of the sheet; and a control system configured to: (i) image the optical fiducials on the fixture; (ii) define an optical reference coordinate system from the imaged optical fiducials; (ii) receive a mathematical model of the glass sheet in a model coordinate system; and (iii) relate the optical reference coordinate system to the model coordinate system via at least one transformation.

2. 10. The system of claim 1, wherein the control system is further configured to: (i) receive image data indicative of the visible wavelength line from the camera; (ii) analyze the data from the camera to determine first and second coordinates in a set of coordinates associated with the line; (iii) triangulate a third coordinate associated with each of the first and second coordinates in the set of coordinates; and (iv) generate a three-dimensional map of the surface of the glass sheet as a function of the set of coordinates.

3. The system of claim 2 , wherein the control system is further configured to transform the three-dimensional map via the at least one transformation and relate the three-dimensional map to the model coordinate system.

4. 4. The system of claim 3, wherein the control system is further configured to output an indicator indicative of a measurement of the glass sheet in response to comparing the three-dimensional map to the mathematical model in the model coordinate system.

5. 5. The system of claim 4, wherein the control system is further configured to determine the index as a simulated light reflectance of the surface using the three-dimensional map of the surface compared to the mathematical model in the model coordinate system.

6. 5. The system of claim 4, wherein the control system is further configured to determine the indicators for gauging the glass sheet using the three-dimensional map of the surface.

7. the control system is further configured to receive a series of data indicative of a series of visible wavelength lines from the camera measured across the width of the sheet, each line corresponding to a different position along a surface of the glass sheet; 5. The system of claim 4, wherein the control system is further configured to analyze each of the series of visible wavelength lines to determine first and second coordinates in a series of coordinates associated with each line, triangulate a third coordinate associated with each of the first and second coordinates in each of the series of coordinates, and create the three-dimensional map of the surface of the glass sheet from each of the series of coordinates.

8. The system of claim 7 , wherein the wavelength of the ultraviolet laser is selected to be non-transparent through the glass sheet.

9. The system of claim 1 , wherein the fixture has a first set of physical references, the first set of physical references having at least three coordinates in the model coordinate system.

10. 10. The system of claim 9, wherein the first set of physical references for the fixture are provided by a calibration surface having a shape corresponding to at least a portion of a surface of the glass sheet.

11. The system of claim 10 , wherein the calibration surface further forms an optical reference.

12. The system of claim 10 , wherein the fixture includes at least one optical fiducial, the at least one optical fiducial being positioned on the calibration surface.

13. The system of claim 12 , wherein the at least one optical reference further provides at least one physical reference.

14. The system of claim 10 , wherein the control system is further configured to determine or derive a transformation from the optical reference coordinate system to the model coordinate system.

15. 10. The system of claim 9, wherein the fixture has a calibration surface shaped to correspond to at least a portion of a surface of a glass sheet provided by exemplary glass sheet G0 to provide a first optical reference.

16. 16. The system of claim 15, wherein the fixture has camera optical fiducials associated with each camera.

17. 17. The system of claim 16, wherein the control system is further configured to image the camera optical fiducials to relate the cameras to each other via at least one other transformation, and to separately image the calibration surface as the optical fiducials to relate the optical reference coordinate system to the model coordinate system via the at least one transformation.

18. 10. The system of claim 9, wherein the control system is configured to determine or receive a transformation relating a physical reference frame of the fixture to the model coordinate system, the transformation being determined using the first set of physical references from the fixture.

19. the optical fiducials define a second set of physical fiducials; 10. The system of claim 9, wherein the control system is configured to image the second set of physical fiducials and relate the second set of physical fiducials to the optical reference coordinate system.

20. 20. The system of claim 19, wherein the control system is configured to determine or receive a transformation relating a physical reference coordinate system of the fixture to a physical reference coordinate system of the optical fiducial, the transformation being determined using the first set of physical references from the fixture and the second set of physical references from the optical fiducial.

21. 20. The system of claim 19, wherein the control system is further configured to determine or receive a transformation relating a physical reference frame of the fixture to the second set of physical references.

22. 22. The system of claim 21, wherein the control system is further configured to determine or derive a transformation from the model coordinate system to the second set of physical references.

23. 23. The system of claim 22, wherein the control system is further configured to determine or derive a transformation from the optical reference coordinate system to the model coordinate system.

24. 2. The system of claim 1, wherein the fixture has a series of standoffs that support the glass sheet, a first datum that positions the glass sheet relative to the fixture, and a second datum that positions the glass sheet relative to the fixture.

25. 1. A method of using a non-contact optical inspection system, comprising: providing a fixture for supporting a glass sheet, the fixture having optical fiducials; imaging the optical fiducials on the fixture via a camera of an inspection assembly; analyzing the imaged optical fiducials via a control system to define an optical reference coordinate system; receiving, via a control system, a mathematical model of the glass sheet in a model coordinate system; and relating, via a control system, the optical reference coordinate system to the model coordinate system via at least one transformation.

26. 26. The method of claim 25, forming a planar laser sheet from an ultraviolet laser and associated optics of the inspection assembly toward a surface of the glass sheet on the fixture; exciting a surface of the glass sheet at an intersection of the planar laser sheet and the surface to form a visible wavelength line on the surface of the glass sheet; imaging the visible wavelength line using the camera; determining first and second coordinates in a set of coordinates associated with the visible wavelength line by analyzing imaging data from the camera; determining by triangulation a third coordinate associated with each of the first and second sets of coordinates associated with the visible wavelength line; and generating a three-dimensional map of the surface of the glass sheet as a function of the set of coordinates.

27. 27. The method of claim 26, transforming the three-dimensional map via the at least one transformation to relate the three-dimensional map to the model coordinate system; calculating a constant index using the three-dimensional map in comparison with a mathematical model of the surface in the model coordinate system; and outputting the constant index.

28. 28. The method of claim 27, wherein the at least one transformation is defined as at least one transformation matrix.

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