Imaging System for Surface Inspection

Abstract

An imaging system and method for evaluating non-uniformities or irregularities in a reflective display, such as an assembled display module of the type found in smart phones, tablet devices, and the like. The system includes unpolarized and collimated incoherent light, such as light emitting diodes (LEDs). The surface to be evaluated is perpendicular to the collimated light such that the light strikes directly on the surface. The polarization of the light is changed before and after reflection, and the reflected light from the surface under evaluation is received by a sensor. Non-uniformities or irregularities of the surface will appear as contrast variations in the sensed image. Since the reflection from the surface under evaluation is a 180-degree reflection, the sensed image can be clearly focused across the entire surface to be evaluated. Optionally, for efficiency and compactness, the system can utilize a single collimating lens without a collection lens.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit under Title 35, U.S.C. § 119(e) of the title of the U.S. Provisional Patent Application Ser. No. 62 / 883,924, entitled "IMAGING SYSTEM FOR SURFACE INSPECTION", filed on Aug. 7, 2019, the entire disclosure of which is hereby expressly incorporated herein by reference. and under § 119(e) of Title 35, United States Code, the entire disclosure of which is hereby expressly incorporated herein by reference. TECHNICAL FIELD

[0003] This application relates to testing and detecting surface irregularities of flat and reflective optical elements and displays, and more particularly, to the evaluation of the flatness or regularity of displays and assembled display modules. BACKGROUND ART

[0004] The waviness or lack of flatness of a flat panel display is an important parameter for providing insight into the lamination process control and for providing an indication of the final product quality. For display modules, having consistent high flatness (i.e., flatness) is becoming increasingly important. End users of display modules can see irregularities (e.g., waviness) in the flatness, especially when viewed at a particular angle. The waviness or other irregularities will thus degrade the user experience.

[0005] What is needed is an improvement over the foregoing. SUMMARY OF THE INVENTION

[0006] The present disclosure relates to an imaging system and method for evaluating non-uniformities or irregularities in a reflective display, such as an assembled display module of the type found in smart phones, tablet devices, etc. The system includes unpolarized incoherent light, such as a light emitting diode (LED). The surface to be evaluated is perpendicular to the incoming light such that the light strikes directly on the surface. The polarization of the light is changed before and after reflection, and the reflected light from the surface under evaluation is received by a sensor to form an image. The non-uniformities or irregularities of the surface will appear as contrast variations in the sensed image. Since the reflection from the surface under evaluation is a 180-degree reflection, the sensed image can be clearly focused across the entire surface to be evaluated. Optionally, for efficiency and compactness, the system can utilize a single collimating lens without a collecting lens.

[0007] In a first system and method, incoherent light passes through a polarization beam splitter and is directed (i.e., perpendicularly) onto a surface to be evaluated, which may be an assembled display module. Light reflected from the display module has its polarization rotated 90 degrees and is then reflected by the polarization beam splitter by 90 degrees. The light then passes through a knife edge or aperture in its path to a camera or imaging sensor, which images the display module via the reflected light. Any non-uniform surface irregularities produce contrast variations in the image of the display module, which facilitates visualization of any irregularities in the surface being evaluated.

[0008] In a second system and method, incoherent light passes through a first linear polarizer, then through an unpolarized beam splitter, and is then directed (i.e., perpendicularly) onto a surface to be evaluated, which may be an assembled display module. Light reflected from the display module has its polarization rotated 90 degrees and is then reflected by the unpolarized beam splitter. The light then passes through a second polarizer and a knife edge or aperture in its path to a camera or imaging sensor, which images the display module via the reflected light. Any non-uniform surface irregularities produce contrast variations in the image of the display module, which facilitates visualization of any irregularities in the surface being evaluated.

[0009] In a third method, a similar arrangement to the second method is used, where a cylindrical lens is added after the collimating lens such that it generates a 1D converging wavefront. When the radius of the wavefront is the same as the radius of the curved surface to be evaluated, this geometry can generate the same Schlieren-type image as used in the first and second methods and apparatuses, since the reflected light from the surface being evaluated will follow the same ray path as the reflection from the flat display above after passing through the cylindrical lens both before and after reflection.

[0010] In one embodiment, the present disclosure provides an imaging system that includes an incoherent light source that emits an incoherent light signal; a collimating lens positioned to receive either the incoherent light signal or a first light signal, the collimating lens emitting a collimated light signal; a polarizer functionally disposed between the incoherent light source and the sensor, and the sensor having a sensor lens that defines a sensor lens plane, the sensor lens plane being positioned generally perpendicular to the incoherent light signal emitted by the light source, the sensor being positioned to receive the reflection of the collimated light signal.

[0011] In another embodiment, the present disclosure provides a method for evaluating defects in an evaluation surface, the method comprising: emitting an incoherent optical signal; passing the incoherent optical signal through a beam splitter to produce a first optical signal and a second optical signal, the first optical signal being angled relative to the second optical signal; passing at least a portion of the incoherent optical signal through a collimating lens to produce a collimated optical signal; reflecting the collimated optical signal off the evaluation surface to produce a reflected optical signal, the evaluation surface defining an evaluation surface plane that is generally perpendicular to the collimated optical signal; and sensing the reflected optical signal on a sensor to produce a sensed image. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above and other features and objects of the present invention and the manner of attaining them will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, in which:

[0013] Figure 1 is a schematic diagram of a first surface irregularity detection system made in accordance with the present disclosure, which utilizes two lenses and a polarization beam splitter;

[0014] Figure 2 is a schematic diagram of a second surface irregularity detection system made in accordance with the present disclosure, which utilizes a single collimating lens, at least one linear polarizer, and a non-polarizing beam splitter;

[0015] Figure 3 is Figure 2 a schematic diagram of the system shown, which has a replacement arrangement in which the sensor and the light source are interchanged;

[0016] Figure 4 is Figure 3 a schematic diagram of the system shown, which has a replacement arrangement in which a cylindrical lens is used to evaluate a curved display module;

[0017] Figure 5 is a flowchart showing a method for evaluating perfection in an evaluation surface in accordance with the present disclosure;

[0018] Figure 6A is a perspective exploded view of a display module in accordance with the present disclosure; and

[0019] Figure 6B is Figure 6A a schematic diagram of the display module shown.

[0020] Throughout several views, corresponding reference numerals indicate corresponding parts. Although the exemplary embodiments set forth herein illustrate embodiments of the invention, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed. DETAILED DESCRIPTION

[0021] The present disclosure relates to a method for inspecting and evaluating the waviness or other surface irregularities of a display module using schlieren-type imaging. A test object is directly (i.e., vertically) exposed to incoherent light that has been linearly polarized and collimated. The conditioned light signal is then reflected from a reflective surface on the test object or integrated into the test object, and the reflected light polarization is rotated 90 degrees by passing twice through a transparent quarter-wave plate laminated into a polarizer laminated onto the display module. An imaging camera images the reflected light signal after further polarization filtering of the light signal. Since the plane of the evaluation surface of the test object is presented directly to the light signal and is parallel to the lens of the imaging camera, the evaluation image is undistorted and can thus be clearly focused across the entire area being evaluated. This in turn results in a very effective and efficient detection and quantification of waviness or other irregularities.

[0022] Figures 1 - 4 Block diagrams of irregularity detection systems 10, 110, 110', 210 are shown, all of which are configured to detect surface irregularities, thickness variations, and / or variations and refractive indices of transparent optical materials (e.g., cover glass or touch panels of the type used in smart phones and tablet devices, display cover glass, films, optical film materials, etc.). Each of systems 10, 110, 110' and 210 utilizes the schlieren imaging principle to detect surface irregularities caused by variations in flatness (or nominal curvature in the case of Figure 4 ), thickness variations, and / or refractive index variations of a transparent optical material. Thus, the irregularity detection systems 10, 110, 110' and 210 can be utilized to detect and analyze the presence and extent of surface waviness or irregularities in an evaluation surface.

[0023] Now turning to Figure 1 , the irregularity detection system 10 utilizes a folded schlieren imaging system in which a polarization beam splitter 16 splits the optical path and effects polarization conversion to image the illumination profile of an object such as display module 50.

[0024] Specifically, an uncollimated or incoherent light source 12, which can be, for example, an LED lamp, emits an incoherent light signal 30, which is then collimated by a collimating lens 14. The resulting collimated light signal 32 passes through the polarization beam splitter 16 to produce a P-polarized light signal 34.

[0025] Then, the display module 50 reflects the P-polarized light signal 34 by 180 degrees, thereby forming a two-pass circular polarizer 18 including a quarter-wave plate and a linear polarizer. The light reflected from the linear polarizer passes twice through the quarter-wave plate. In the illustrated embodiment, the circular polarizer 18 is integrated into the display module 50. The resulting signal reflected from the display module 50 is an S-polarized light signal 36, which re-enters the polarization beam splitter 16 and is reflected again, this time by 90 degrees, to become a reflected light signal 38 that remains S-polarized.

[0026] The reflected light signal 38 then passes through the collection lens 20, thereby remaining in the S-polarized signal configuration. The resulting collected light signal 40 is then directed to an imaging lens 22, which has an aperture stop positioned at the focal point of the collected light signal 40. Alternatively, the aperture stop in the imaging lens can be replaced by a knife edge 22, which is positioned to filter the collected light signal 40 at the focal point. The resulting filtered light signal 42 is then received by a sensor 24, which can collect and present an image indicative of the surface regularity of the reflective surface to be evaluated. In the illustrated embodiment, as shown and described herein, the evaluation surface is from the display module 50.

[0027] In the case where there is waviness or other irregularities in the evaluation surface, the detection system 10 causes the incoming rays of the collected light signal 40 to be blocked by the opaque portion of the aperture stop or the knife edge, while the cleanly reflected rays pass through the aperture stop or the knife edge. In this way, the system 10 creates a contrast change in the reflected image of the evaluation surface, as aggregated and output by the sensor 24 (e.g., to a monitor or other display module). This contrast change indicates the presence and extent of the waviness or surface irregularities of the evaluation surface, where a larger contrast change corresponds to a greater prevalence and / or magnitude of other irregularities, and vice versa.

[0028] Now turning to Figure 2 , a second irregularity detection system 110 is illustrated, which facilitates the detection and quantification of waviness or other irregularities in a manner similar to the system 10 described above. The system 110 is generally similar to the system 10 described above, where the reference numerals of the system 110 are similar to those used in the system 10, except that 100 is added to those of the system 10. Unless otherwise stated, the elements of the system 110 correspond to the similar elements represented by the corresponding reference numerals of the system 10.

[0029] However, the system 110 is reconfigured to eliminate the collection lens 20, such that the system 110 can be more physically compact and less expensive.

[0030] In system 110, an incoherent light source 112 emits an incoherent optical signal 130, which passes through a first linear polarizer 126 to produce a P-polarized optical signal 134. The optical signal 134 then passes through an unpolarized beam splitter 116 and a collimating lens 114 to produce a collimated optical signal 132 that is directed perpendicularly and directly towards the display module 50. That is, the collimated optical signal 132 is perpendicular to the plane of the evaluation surface of the display module 50. The signal 132 passes twice through a quarter-wave plate that is included as part of a circular polarizer 118, which may be constructed similarly to the polarizer 18 described above.

[0031] The resulting reflected optical signal emitted from the display module 50 is an S-polarized optical signal 136, which is oriented 180 degrees with respect to the P-polarized collimated optical signal 132. The signal 136 is directed back towards the unpolarized beam splitter 116, which reflects the signal 136 by 90 degrees. The resulting reflected optical signal 138 then passes through a second linear polarizer 128, and the resulting S-polarized signal encounters an imaging lens 122 with an aperture stop positioned at the focal point. As discussed above with respect to system 10, this aperture stop (or knife edge) at the focal point causes any light rays reflected by non-flat portions of the reflective surface of the display module 50 to be blocked by the opaque portion of the aperture stop, thereby creating a contrast with the light rays reflected from the flat surface portions. Thus, the image collected by the sensor 124 via the optical signal 142 provides a contrast that indicates the presence, orientation, and magnitude of waviness or other surface irregularities in the evaluation surface of the display module 50.

[0032] Figure 3 An irregularity detection system 110’ is shown, which is generally similar in structure and function to the irregularity detection system 110 described in detail above. As shown, systems 110 and 110’ are generally similar to each other and are composed of the same constituent structures.

[0033] However, the detection system 110’ interchanges the orientation of the light source 112 and the sensor 124 along with other associated components (such as the aperture stop 122 and the linear polarizers 126 and 128) with respect to the beam splitter 116. As Figure 3 depicted, an incoherent light source 112 emits an incoherent optical signal 130, which passes through a linear polarizer 126 to produce a P-polarized optical signal 134. The signal 134 is then reflected 90 degrees by the unpolarized beam splitter 116. The resulting reflected signal 138 passes through the collimating lens 114, thereby producing a collimated optical signal 132 that is reflected from the display module 50 via the circular polarizer 118 in the same manner as described above with respect to system 110.

[0034] The reflected S-polarized light signal 136 emitted by the evaluation surface of the display module 50 then passes through the non-polarizing beam splitter 116, and through the second linear polarizer 128. The imaging lens (or knife edge) 122 filters the S-polarized light signal 136, and the resulting light signal 142 is received by the sensor 124. As described above, the resulting image sensed by the sensor 124 has a contrast that indicates the presence and extent of surface irregularities.

[0035] Reference now Figure 4 , the irregularity detection system 210 has a generally similar configuration to the system 110' described above. In addition, the system 210 is substantially similar to the systems 110 and 110' described above, wherein the reference numerals of the system 210 are similar to the reference numerals used in the systems 110 and 110', except that 100 is added to the system 210. Unless otherwise specified, the elements of the system 210 correspond to similar elements represented by corresponding reference numerals of the system 110.

[0036] However, the irregularity detection system 210 further includes a cylindrical lens 215 that receives the collimated light signal 232 from the collimating lens 214. The cylindrical lens 215 transmits the P-polarized focused light signal 240 toward the curved display module 250 including the circular polarizer 218. After reflection and double-passing through the polarizer 218, the light signal 236 is reflected from the curved evaluation surface when passing back through the cylindrical lens 215 and the collimating lens 214 to generate a reflected light signal 238.

[0037] The converged light signal 240 is a one-dimensional curved (i.e., focused) wavefront that is incident on a corresponding convexly curved reflective surface of the display 250. The radius of curvature of the focused wavefront is equal to the intended radius of the curved convex display surface of the display module 250, so that the reflected S-polarized light signal 236 reflected by the evaluation surface of the module 250 passes back through the cylindrical lens 215 to become re-collimated, and then passes back through the collimating lens 214 to become re-focused toward the sensor 224 as a reflected light signal 238. Thus, the cylindrical lens operates to produce a reflected light signal 238 from the curved surface of the curved display module 250, which has the same schlieren image configuration as the systems 10, 110, and 110' designed for evaluating flat surfaces as described in detail above. In this way, the presence and extent of irregularities of the curved evaluation surface can be assessed the same as for a flat (i.e., planar) surface.

[0038] exist Figure 4In the illustrated embodiment, the cylindrical lens 215 is a positive (i.e., focusing) cylindrical lens that is designed for use with a convexly curved display as described above. However, a similarly formed negative cylindrical lens can also be used to generate a similar one-dimensional diverging wavefront that is designed for accurately measuring irregularities in a curved concave display panel.

[0039] Figure 4 Illustrated is that the light source 212 emits a P-polarized light signal 234 towards the reflective surface of the non-polarizing beam splitter 216 via the linear polarizer 226, while the reflected light signal 238 is directed towards the sensor 224 through the beam splitter 216. Except for adding the cylindrical lens 215 and the system 210, this configuration is similar to Figure 3 the system 110’ shown and discussed in detail above. However, it is also contemplated that Figure 2 the configuration of the system 110 shown can be similarly modified by adding a cylindrical lens 215 for evaluating the curved display module 250. That is, the light source 212 and the sensor 224 can be interchanged with their associated components with respect to the beam splitter 216.

[0040] In Figure 1 and Figure 2 the cases of the systems 10 and 110 shown respectively, the light sources 12, 112 directly irradiate the display module 50. That is, the collimated light beams derived from the light sources 12, 112 are perpendicular to the plane defined by the surface of the display module 50 to be evaluated. For the purposes of this disclosure, “substantially perpendicular” refers to approximately 90 degrees, such as angles as small as 89.5 degrees, 89.7 degrees or 89.9 degrees, or as large as 90.1 degrees, 90.3 degrees or 90.5 degrees, including the exact 90 degrees, or any angular range defined by any pair of the foregoing values.

[0041] In contrast, in Figure 3 and Figure 4 the cases of the systems 110’ and 210 shown, the incoherent light sources 112, 212 emit incoherent light signals 130, 230 that are nominally parallel to the respective evaluation surface planes of the display modules 50 and 250, but after being reflected and collimated from the non-polarizing beam splitters 116, 216, the collimated light beams again directly irradiate (i.e., are perpendicular to) the plane defined by the evaluation surface.

[0042] In this manner, all systems 10, 110, 110', and 210 are arranged such that, with respect to the planes defined by the respective lenses of sensors 24, 124, and 224, they are perpendicular to the incoming filtered signals 42, 142, 242, respectively. This incoming signal is in turn a direct reflection of the reflective surface display module 50 or 250. Thus, sensors 24, 124, and 224 are positioned to receive a reflected collimated light signal that is a direct 180-degree reflection of the plane of the evaluation surface of display modules 50, 250. Thus, all resulting images generated by sensors 24, 124, and 224 can be in perfect or near-perfect focus. In contrast, in systems where the reflected image received by the sensor comes from a display module angled with respect to the sensor lens, perfect focus is possible only across a narrow strip of the reflected image.

[0043] In the case of systems 10, 110, and 110', the evaluation surface is a substantially planar surface because display module 50 presents a nominally planar surface display to the user. For the purposes of this disclosure, and in the context of mobile phones and handheld tablet devices, "substantially planar" can mean a surface having a nominal variation from planarity of no greater than 100 µm. For these systems, the contrast in the image received by sensor 24 or 124 indicates non-planarity or other irregularities of the evaluation surface.

[0044] On the other hand, Figure 4 System 210 is shown as being designed to evaluate the curved surface of display module 250 as described above. It can still be said that this curved surface defines a plane similar to the plane of inspection of the planar surface of display module 50. For the purposes of this disclosure, the plane of the evaluation surface of curved module 250 is the plane perpendicular to the radius of curvature defined by the curved surface and bisecting the surface area to be evaluated such that one half of the curved surface is on one side of the plane and the other half of the curved surface is on the other side of the plane. In Figure 4 system 210, the image sensed by sensor 224 indicates defects in the curvature of the evaluation surface, where a "perfect" surface represents a surface that perfectly conforms to a desired cut arc (e.g., cylindrical or spherical) surface, and a defect represents a deviation from this perfect surface.

[0045] Figure 5 An exemplary method for evaluating defects in an evaluation surface is illustrated, whether a planar surface (in the case of systems 10, 110, or 110') or a curved surface (in the case of system 210). This method 300 can be carried out by a human user of a system made in accordance with this disclosure or can be automated by using a computer or controller.

[0046] In an embodiment, the images detected by sensors 24, 124, or 224 are evaluated by a controller. In an embodiment, the controller is microprocessor-based and includes a non-transitory computer-readable medium that includes processing instructions stored therein, the processing instructions being executable by the microprocessor of the controller to evaluate the detected images to determine the level of defects in the display surface under test. The non-transitory computer-readable medium or memory may include random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (e.g., EPROM, EEPROM, or flash memory), or any other tangible medium capable of storing information.

[0047] The images will be processed by software designed to detect and evaluate contrast changes and determine the defect size and generate a score for the overall display quality. Both conventional image processing and machine learning techniques can be used to implement the software.

[0048] In step 310, an incoherent optical signal is emitted, such as by applying electrical energy to a light source. In an exemplary embodiment, the optical signal is an LED signal from one of light sources 12, 112, or 212. In step 320, the incoherent optical signal passes through a beam splitter, such as polarization beam splitter 16 or non-polarizing beam splitter 116 or 216, to produce a first optical signal and a second optical signal that are angled with respect to each other. In one exemplary embodiment, the first and second optical signals may be at an angle of 90° with respect to each other and split approximately 50 / 50 such that each of the first and second optical signals has equal or substantially equal intensity. The light passing directly through the polarization beam splitter is linearly polarized in a first direction and is referred to herein as p-polarized. In the case of a non-polarizing beam splitter, the light is not polarized by the beam splitter.

[0049] In step 330, at least a portion of the incoherent optical signal passes through a collimating lens to produce a collimated optical signal. In some systems made in accordance with the present disclosure (such as system 10), this collimation step may occur before the incoherent optical signal enters the beam splitter. In other systems made in accordance with the present disclosure, such as in systems 110, 110', and 210, this step may occur after the optical signal has passed through the beam splitter or has been reflected by the beam splitter. As such, in some cases, only a portion of the incoherent optical signal may pass through the collimating lens.

[0050] In step 340, at least a portion of the incoherent optical signal is polarized. Such polarization can be affected by one or more structures including polarization beam splitter 16 in system 10, linear polarizers 126, 128 in systems 110, 110', or linear polarizers 226 and 228 in system 210. Additionally, each of systems 10, 110, 110', and 210 can affect the polarization of at least a portion of the incoherent optical signal via circular polarizer 18, 118, or 218, respectively, either before or after collimation.

[0051] In step 350, the collimated optical signal is reflected off an evaluation surface (such as the reflective surface of display module 50 or 250) to produce a reflected optical signal. The reflected optical signal is sensed by a sensor (such as sensor 24, 124, or 224) to produce a sensed image. In step 370, the sensed image is used for contrast evaluation to determine the presence and magnitude of surface irregularities in the evaluation surface.

[0052] In an exemplary embodiment, display modules 50, 250 can be a mobile phone, a tablet device, or other handheld display device, and systems 10, 110, 110', or 210 are used to evaluate the operator interface of the mobile phone or tablet device. For example, Figure 6A and Figure 6B illustrates mobile phone 400 that can replace display module 50 or 250 (depending on whether phone 400 has a nominally flat or nominally curved user interface).

[0053] As Figure 6A shown, mobile phone 400 includes a back cover 410. Bottom case 420 mates with face case 430 to protect circuit board 425, which is configured to provide functionality to mobile phone 400. Bottom case 420 is configured to support battery 415 and is further configured to mate with back cover 410. Face case 430 is configured to mate with and support display module 440. When fully assembled, display module 440 includes display layer 470 and cover glass / touch panel 450a. Cover glass / touch panel 450a is configured as transparent material or transparent optical material 450. When all the various components are mated together, mobile phone 400 is configured in a convenient package suitable for handling by a human hand. Except for having a larger overall size, a tablet device can be configured similarly to phone 400.

[0054] The display module 440 includes: a display layer 470, such as a liquid crystal display (LCD), a circular polarizer 460, and an optically transparent cover glass / touch panel 450a. In some configurations, as shown by the dashed outline surrounding both the display layer 470 and the circular polarizer 460, the circular polarizer 460 can be integrated within the display layer 470. The display layer 470 is configured to provide a visual interface to a corresponding user, such as by displaying an image viewable by the user. As required or desired by a particular application, the display layer 470 can include one or more additional layers. Various techniques are used to construct the display layer 470, which is generally configured to provide pixels of color light viewable by the user. These techniques include: liquid crystal displays (LCDs), light emitting diodes (LEDs), organic light emitting diodes (OLEDs), etc. The cover glass / touch panel 450a is located adjacent to the display layer 470 or the circular polarizer 460 associated with the display layer 470. The cover glass / touch panel 450a is configured as a user interface, where a user can interact with the mobile phone 400 and / or provide input control by using a stylus or one or more fingers to touch the glass or panel 450a.

[0055] Other uses of the display module 440 and / or the transparent optical material 450 are envisioned, such as any mobile device having a display screen, a television screen, a computer monitor, a tablet device, an integrated display screen (e.g., integrated into an automotive dashboard, a desktop, a panel, etc.), a portable communication device, etc.

[0056] In particular, for an optimal viewing experience of the user, uniformity of the top surface 451 of the cover glass / touch panel 450a and the top surface 471 of the display layer 470 is desired. Embodiments of the present disclosure (including the systems 10, 110, 110', and 210 described in detail above) are configured to detect and / or measure the flatness of the top surface 451 of the cover glass 450a or other transparent material and the top surface 471 of the display layer 470 or other reflective material.

[0057] Although the present invention has been described as having an exemplary design, the present invention can be further modified within the spirit and scope of the present disclosure. Accordingly, this application is intended to cover any variations, uses, or adaptations of the present invention using its general principles. Additionally, this application is intended to cover such departures from the present disclosure within the scope of known or customary practice in the art to which the present invention pertains and falling within the limitations of the appended claims.

Claims

1. An imaging system, comprising: An incoherent light source that emits an incoherent optical signal; A collimating lens that is positioned to receive the incoherent optical signal, and the collimating lens emits a collimated optical signal; A sensor having a sensor lens including an aperture, the sensor lens defining a sensor lens plane, and the sensor is positioned to receive the reflection of the collimated optical signal; A polarizer that is functionally disposed between the incoherent light source and the sensor; And A display module, comprising: A display layer, An optically transparent cover glass, and A circular polarizer for rotating the polarization of the collimated optical signal by 90 degrees, The display module has an evaluation surface defining an evaluation surface plane, and the display module is positioned such that the evaluation surface plane is substantially perpendicular to the collimated optical signal.

2. The imaging system according to claim 1, wherein, The sensor lens plane is substantially parallel to the evaluation surface plane.

3. The imaging system according to claim 1, wherein, The sensor lens plane is substantially perpendicular to the evaluation surface plane.

4. The imaging system according to claim 1, wherein, The evaluation surface is a substantially planar surface, whereby the image sensed by the sensor includes a contrast indicating the non-planarity of the evaluation surface.

5. The imaging system according to claim 1, wherein, The evaluation surface is a curved surface, and the imaging system further includes a cylindrical lens having a curvature corresponding to the curvature of the curved surface, whereby the image sensed by the sensor includes a contrast indicating a defect in the curvature of the evaluation surface.

6. The imaging system according to claim 1, further comprising: A beam splitter that is positioned to split the incoherent optical signal into a first optical signal and a second optical signal, the first optical signal being angled relative to the second optical signal.

7. The imaging system according to claim 6, wherein, The polarizer includes: A first linear polarizer disposed between the incoherent light source and the beam splitter, wherein the beam splitter includes an unpolarizing beam splitter; and A second linear polarizer disposed between the sensor and the beam splitter.

8. The imaging system according to claim 6, wherein, The beam splitter and the polarizer are combined as a polarization beam splitter.

9. The imaging system according to claim 8, further comprising a collection lens disposed between the polarization beam splitter and the sensor.

10. The imaging system according to claim 1, wherein, The incoherent optical signal is emitted by a light-emitting diode.

11. A method for evaluating a defect in an evaluation surface, the method comprising: Emitting an incoherent optical signal; Passing the incoherent optical signal through a beam splitter to produce a first optical signal and a second optical signal, the first optical signal being angled relative to the second optical signal; Passing at least a portion of the incoherent optical signal through a collimating lens to produce a collimated optical signal; Reflecting the collimated optical signal on an evaluation surface of a display device to produce a reflected optical signal, wherein the display device includes a display module, the display module including: a display layer, an optically transparent cover glass, and a circular polarizer for rotating the polarization of the collimated optical signal by 90 degrees, the evaluation surface defining an evaluation surface plane substantially perpendicular to the collimated optical signal; and Sensing the reflected optical signal on a sensor to produce a sensed image, the sensing including passing the reflected optical signal through the aperture of a sensor lens.

12. The method according to claim 11, further comprising: Evaluating the contrast in the sensed image to determine the presence and magnitude of surface irregularities of the evaluation surface.

13. The method according to claim 12, wherein, The evaluation surface is a curved surface, and the method further includes: Passing the collimated optical signal through a cylindrical lens to produce a modified collimated optical signal, The reflecting step includes reflecting the modified collimated optical signal on the curved evaluation surface, and The steps of evaluating contrast include determining the presence and extent of defects in the curvature of a curved evaluation surface.

14. The method according to claim 12, wherein: the evaluation surface is a substantially planar surface, and the steps of evaluating contrast include determining the presence and extent of non-planarity of the substantially planar surface.

15. The method according to claim 11, further comprising at least one of a polarized incoherent optical signal, a portion of the incoherent optical signal, and a collimated optical signal.

16. The method according to claim 11, further comprising: positioning a collimating lens substantially perpendicular to at least a portion of the incoherent optical signal; and positioning the evaluation surface substantially parallel to the collimating lens.

Images