JP2022153463A - Imaging system for surface inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging system and a method for evaluating heterogeneity or non-uniformity in a reflective display such as assembled display modules of a type found in smartphones, tablets and the like.

SOLUTION: A system includes incoherent light such as a light-emitting diode (LED) which is polarized and collimated. A surface to be evaluated is perpendicular to the collimated light, thereby the light hits directly on the surface. Polarization of the light is altered before and after reflection, and the reflected light from the surface to be evaluated is received by a sensor. Heterogeneity or non-uniformity of the surface will appear in a sensed image as contrast variation. Because reflection from the surface to be evaluated is 180 degrees reflection, the sensed image can be in sharp focus across the entire surface to be evaluated. Optionally, the system may utilize a single collimation lens without a collection lens for efficiency and compactness.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

This application claims the benefit, under 35 U.S.C. The entire disclosure of which is expressly incorporated herein by reference.

This application relates to the testing and detection of surface unevenness in flat reflective optical elements and displays. More particularly, it relates to evaluating the planarity or uniformity of displays and assembled display modules.

The relief, or lack of planarity, of a flat panel display is an important parameter for providing insight into lamination process control and for providing an indication of final product quality. It is becoming increasingly important that display modules have a uniformly high planarity (ie flatness). Non-uniformities in planarity (eg, undulations) may be noticed by the end user of the display module, especially when viewed at certain angles. Any undulations or other unevenness will result in a poor user experience.

Improvements to the above are needed.

The present disclosure is directed to imaging systems and methods for evaluating non-uniformity or non-uniformity in reflective displays such as assembled display modules of the type found in smart phones, tablets, and the like. This system includes incoherent light, such as a polarized light emitting diode (LED). The surface to be evaluated is perpendicular to the incident light, so the light impinges 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. Surface non-uniformities or unevenness appear as contrast variations in the sensed image. Since the reflection from the surface under evaluation is a 180° reflection, the sensed image can be sharply focused over the surface to be evaluated. Optionally, the system may utilize a single collimation lens without a collection lens for efficiency and compactness.

In the first system and method, incoherent light passes through a polarizing beam splitter and shines directly (ie vertically) on the surface to be evaluated. The surface to be evaluated can be an assembled display module. The light reflected from the display module has its polarization switched 90° and then reflected 90° by the polarizing beam splitter. The light then passes through a knife edge or aperture in its path to a camera or imaging sensor. A camera or imaging sensor projects an image onto the display module via reflected light. Any uneven surface unevenness creates a contrast change in the image of the display module, which facilitates visualization of any unevenness on the evaluated surface.

In a second system and method, the incoherent light passes through a first linear polarizer, then through a non-polarizing beam splitter, and directly (i.e., perpendicularly) onto the surface to be evaluated. Shine. The surface to be evaluated can be an assembled display module. Light reflected from the display module switches polarization by 90° and is then reflected by a non-polarizing 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. A camera or imaging sensor projects an image onto the display module via reflected light. Any uneven surface unevenness creates a contrast change in the image of the display module, which facilitates visualization of any unevenness on the evaluated surface.

In a third method, an arrangement similar to the second method is used with the addition of a cylindrical lens after the collimation lens, thereby producing a 1D focused wavefront. If the radius of the wavefront is the same as the radius of the curved surface to be evaluated, this shape produces the same Schlieren-type image used in the first and second methods and apparatus. can be generated. This is because the reflected light from the surface being evaluated will follow the same light path as the reflection from the flat panel display described above after both pre-reflection and post-reflection through the cylindrical lens.

In one embodiment, the present disclosure provides an incoherent light source that emits an incoherent optical signal, and a collimation lens positioned to receive one of the incoherent optical signal and the first optical signal and emits a collimated optical signal. , a polarizer operatively disposed between an incoherent light source and a sensor. The sensor has a sensor lens defining a sensor lens plane positioned substantially perpendicular to the incoherent light signal emitted from the light source. The sensor is positioned to receive reflections of the collimated optical signal.

In another embodiment, the present disclosure provides a method of evaluating imperfections in an evaluated aspect. The method includes the steps of emitting an incoherent optical signal and 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 the second optical signal. passing at least a portion of the incoherent optical signal through a collimation lens to produce a collimated optical signal; reflecting to produce a reflected light signal, the surface to be evaluated defining a plane of the evaluation surface that is substantially perpendicular to the collimated light signal; and sensing the reflected light signal at a sensor. to produce a sensed image.

The above and other features and objects of the invention, as well as methods of achieving them, will become clearer and the invention itself will become better understood by reference to the following description of the embodiments of the invention in conjunction with the accompanying drawings. be understood by

1 is a schematic diagram of a first surface unevenness detection system made according to the present invention utilizing two lenses and a polarizing beam splitter; FIG. FIG. 4 is a schematic diagram of a second surface unevenness detection system made according to the present invention utilizing a single collimation lens, at least one linear polarizer, and a non-polarizing beam splitter; 3 is a schematic diagram of the system shown in FIG. 2 with an alternative arrangement in which the sensor and light source have been replaced; FIG. FIG. 4 is a schematic diagram of the system shown in FIG. 3 with an alternative arrangement utilized for evaluation of a cylindrical lens curved display module; 4 is a flow chart illustrating a method of assessing the integrity of an assessed surface according to the present disclosure; 1 is an exploded perspective view of a display module according to the present disclosure; FIG. 6B is a schematic diagram of the display module shown in FIG. 6A; FIG.

Corresponding reference characters indicate corresponding parts throughout the drawings. The examples described herein illustrate embodiments of the invention, and the embodiments disclosed below are not intended to be exhaustive or construed to limit the scope of the invention to the precise forms disclosed. not.

The present disclosure is directed to methods for inspecting and evaluating undulations or other surface unevenness of display modules using schlieren-type imaging. The test subject is directly (ie, perpendicularly) exposed to linearly polarized, collimated, incoherent light. This conditioned light signal is then reflected from the reflective surface of the test object or a reflective surface integrated into the test object. The polarization of this reflected light is rotated 90° by a double pass through a clear quarter-wave plate integrated into the polarizer laminated onto the display module. An imaging camera images the reflected light signal after subjecting the light signal to an additional polarizing filter. Since the plane of the surface to be evaluated 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 not distorted and is therefore sharp throughout the area to be evaluated. can be focused. This in turn provides very efficient and effective detection and quantification of undulations or other non-uniformities.

1-4 show block diagrams of non-uniformity detection systems 10, 110, 110', 210. FIG. They are all subject to surface unevenness, thickness variations, and/or transparent optical materials (e.g., cover glass or touch panels of the type used in smartphones or tablets, display cover glass, thin films, optical thin film materials, etc.). is configured to detect the variation and refraction of the Each of systems 10, 110, 110′, and 210 utilizes schlieren imaging principles to detect variations in flatness (or nominal curvature in the case of FIG. 4), variations in thickness, and/or refraction of transparent optical materials. Detects surface unevenness caused by modulus variation. The presence and extent of surface relief or unevenness in the surface being evaluated can thereby be detected and analyzed using the unevenness detection system 10, 110, 110', and 210.

Referring now to FIG. 1, non-uniformity detection system 10 utilizes a folded schlieren imaging system. In a schlieren imaging system, the polarizing beam splitter 16 splits the light path and performs polarization switching to image the illumination profile of an object, such as the display module 50 .

Specifically, a non-collimated or incoherent light source 12 , which may be, for example, an LED fixture, emits an incoherent light signal 30 , which is then collimated by collimation lens 14 . The resulting collimated optical signal 32 is passed through a polarizing beam splitter to produce a P-polarized optical signal 34 .

The P-polarized light signal 34 is then reflected 180° by the display module 50 to create a double-pass circular polarizer 18 that includes a quarter-wave plate and a linear polarizer. Light reflected from the linear polarizer makes a double pass through the quarter-wave plate. In the illustrated embodiment, circular polarizer 18 is integrated into display module 50 . The resulting signal reflected from the display module 50 is the S-polarized light signal 36, which re-enters the polarizing beam splitter 16 and is again reflected, this time by 90°, resulting in the reflected light signal 38, which remains S-polarized. .

The reflected light signal 38 then passes through the collection lens 20, preserving the S-polarized signal configuration. The resulting collected light 40 is then directed to the imaging lens 22 . The imaging lens 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 with a knife edge 22 positioned to filter the collected light signal 40 at the focal point. The resulting filtered optical signal 42 is then received by the sensor 24 . Sensor 24 may collect and present an image indicative of the surface uniformity of the reflective surface to be evaluated. In the illustrated embodiment, the surface being evaluated is from the display module 50 as shown and described herein.

If undulations or other non-uniformities exist in the surface being evaluated, detection system 10 causes the incident light of collected optical signal 40 to be blocked by an aperture stop or knife-edge opaque portion. Clearly reflected light, on the other hand, passes through the aperture stop or knife edge. Thus, system 10 produces contrast variations in the reflected image of the evaluated surface as collected and output by sensor 24 (eg, to a monitor or other display module). This contrast change is an indication of the presence and extent of the surface relief or unevenness being evaluated, with greater contrast changes corresponding to greater extent and/or magnitude of the relief or other unevenness. and vice versa.

Referring now to FIG. 2, a second unevenness detection system 110 is shown that facilitates the detection and quantification of undulations or other unevennesses in a manner similar to system 10 described above. System 110 is substantially similar to system 10 described above. The reference number for system 110 corresponds to the reference number for system 10 plus one hundred. Elements of system 110 correspond to similar elements represented by corresponding system 10 reference numerals, unless otherwise noted.

However, system 110 can be reconfigured without collecting lens 20, thereby making system 100 physically smaller and less expensive.

In system 110 , an incoherent light source 112 emits an incoherent optical signal 130 that passes through a first linear polarizer 126 to produce a P-polarized optical signal 134 . Optical signal 134 then passes through non-polarizing beam splitter 116 and collimating lens 114 to produce collimated optical signal 132 directed orthogonally to display module 50 . That is, collimated light signal 132 is perpendicular to the plane of the evaluated surface of display module 50 . Signal 132 passes through a quarter-wave plate included as part of circular polarizer 118 in a double pass. Circular polarizer 118 may be constructed similarly to polarizer 18 described above.

Emanating from display module 50 , the resulting reflected light signal is S-polarized light signal 136 oriented at 180° from P-polarized collimated light signal 132 . The signal 136 is directed backwards to the non-polarizing beamsplitter 116 and the signal 136 is reflected 90°. The resulting reflected light signal 138 then passes through a second linear polarizer 128 and the resulting S-polarized signal strikes an imaging lens 122 having an aperture stop positioned at the focal point. As described above for system 10, this aperture stop (or knife edge) at the focal point causes any light rays reflected by the non-flat portion of the reflective surface of display module 50 to be blocked by the opaque portion of the aperture stop. This creates contrast for light rays reflected from flat surfaces. Accordingly, the image collected by sensor 124 via light signal 142 provides a contrast indication of the presence, location, and magnitude of relief or other surface unevenness on the evaluated surface of display module 50. .

FIG. 3 shows an inequality detection system 110' that is generally similar in structure and function to the inequality detection system 110 described in detail above. Systems 110 and 110' are substantially similar to each other and are of the same configuration of construction as shown.

However, detection system 110' interchanges the positions of light source 112 and sensor 124 relative to beamsplitter 116, along with other associated components (such as aperture stops and linear polarizers 126 and 128). As represented in FIG. 3, an incoherent light source 112 emits an incoherent optical signal 130 that passes through a linear polarizer 126 to produce a P-polarized optical signal 134 . Signal 134 is then reflected 90° by non-polarizing beamsplitter 116 . The resulting reflected signal 138 passes through collimation lens 114 which produces collimated light signal 132 and is reflected from display module 50 through circular polarizer 118 in the same manner as described above for system 110 .

The reflected S-polarized light signal emitted by the evaluated surface of display module 50 then passes through non-polarizing beam splitter 116 and second linear polarizer 128 . An imaging lens (or knife edge) 122 filters the S-polarized light signal 136 and the resulting light signal 142 is received by sensor 124 . The resulting image sensed by sensor 124 has a contrast indication of the presence and extent of surface unevenness as described above.

Referring now to FIG. 4, non-uniformity detection system 210 has a configuration generally similar to system 110' described above. Further, system 210 is substantially similar to systems 110 and 110' described above, and the reference number for system 210 corresponds to the reference number for systems 110 and 110' plus one hundred. Elements of system 210 correspond to similar elements represented by corresponding reference numbers in system 110 unless otherwise noted.

However, nonuniformity detection system 210 further includes cylindrical lens 215 that receives collimated optical signal 232 from collimation lens 214 . Cylindrical lens 215 passes the P-polarized converging optical signal 240 towards a curved display module 250 containing circularly polarized light 218 . After reflection and double pass through polarizer 218 , optical signal 236 reflects off the curved surface being evaluated and passes back through cylindrical lens 215 and collimation lens 214 to produce reflected optical signal 238 .

The converging optical signal 240 is a one-dimensional curved (ie, focal) wavefront that is incident on a corresponding convexly curved reflective surface of the display 250 . The radius of curvature of this focal wavefront is equal to the intended radius of the curved convex display surface of display module 250 . As such, the S-polarized optical signal 236 reflected by the evaluated surface of the module 250 passes back through the cylindrical lens 215 and is re-collimated. It then returns through collimation lens 214 and is refocused as reflected light signal 238 onto sensor 224 . The cylindrical lens thereby operates to create a reflected light signal 238 from the curved surface of the curved display module 250 . Curved display module 250 is of the same schlieren image configuration as systems 10, 110, and 110' designed for evaluation of flat surfaces detailed above. In this way, the presence and extent of non-uniformities in curved evaluated surfaces can be investigated in the same way as for flat surfaces (ie, planes).

In the embodiment shown in FIG. 4, cylindrical lens 215 is a positive (ie, focusing) cylindrical lens designed for use with convexly curved displays as described above. However, a similarly formed negative cylindrical lens can also be designed for accurate measurement of the unevenness of curved convex display panels and can be used to generate a wavefront spreading in one dimension as well. .

FIG. 4 shows a light source 212 emitting a P-polarized optical signal 234 through a linear polarizer 226 toward a reflective surface of a non-polarizing beamsplitter 216 . Meanwhile, reflected light signal 238 passes through beam splitter 216 to sensor 224 . This configuration is similar to system 110' shown in FIG. 3 and described in detail above, except that cylindrical lens 215 and system 210 are added. However, the configuration of system 110 shown in FIG. 2 may be similarly modified with the addition of cylindrical lens 215 for curved display module 250 evaluation. That is, light source 212 and sensor 224 can be replaced with their associated components relative to beamsplitter 216 .

For the systems 10 and 110 shown in FIGS. 1 and 2 respectively, the light sources 12 , 112 shine directly on the display module 50 . That is, the collimated 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. "Substantially perpendicular" for the purposes of this disclosure refers to about 90°, at least 89.5°, 89.7°, or 89.9°, or at most 90.1°, 90.3° , or 90.5°, including exactly 90°. or any angular range defined by any pair of the aforementioned values.

Conversely, for the systems 110' and 210 shown in FIGS. 3 and 4, the incoherent light sources 112,212 emit incoherent optical signals 130,230. Although they are nominally parallel to the surface being evaluated of display modules 50 and 250, respectively, after reflection from the non-polarizing beam splitters 116, 216 and collimation, the collimated light beams are directed to the surface being evaluated. shines directly (i.e. vertically) on the plane defined by

Thus, all of systems 10, 110, 110', and 210 ensure that the planes defined by the lenses of sensors 24, 124, and 224, respectively, are filtered incident signals 42, 142, 242, respectively. positioned perpendicular to the This incident signal is a direct reflection of the reflective surface of display module 50 or 250 . Accordingly, sensors 24, 124, and 224 are positioned to receive the reflected collimated optical signal. The reflected collimated light signal is a direct 180° reflection in the plane of the evaluated surface of the display module 50,250. Accordingly, the resulting images produced by sensors 24, 124, and 224 are perfectly or nearly perfectly in focus. Conversely, 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 only possible over a narrow strip of reflected image.

For systems 10, 110, and 110', the surface being evaluated is substantially planar, and display module 50 presents a nominally planar display to the user. For the purposes of this disclosure, "substantially planar" in the context of mobile phones and handheld tablet devices may mean a surface with a nominal variation of 100 μm or less from flatness. For these systems, the contrast in the image received by sensor 24 or 124 represents unevenness or other unevenness of the surface being evaluated.

FIG. 4, on the other hand, shows a system 210 designed for evaluation of curved surfaces of a display module 250 as described above. This curved surface may define a plane of inspection similar to the flat surface of display module 50 . For the purposes of this disclosure, the plane of the evaluated surface of the curved module 250 is the plane perpendicular to the radius of curvature defined by the curved surface and bisecting the area of the surface to be evaluated. is. Thereby half of the curved surface lies on one side of the plane and the other half of the curved surface lies on the other side of the plane. In system 210 of FIG. 4, the image sensed by sensor 224 represents the curvature imperfections of the evaluated surface. A "perfect" surface refers to a surface that perfectly fits the desired rounded (eg, cylindrical or spherical) surface, and imperfections refer to deviations from that perfect surface.

FIG. 5 shows an exemplary method for assessing imperfections in the evaluated surface, either planar (for system 10, 110, or 110′) or curved (for system 210). . This method 300 can be performed by a user of a system made according to the present disclosure or can be automated through the use of a computer or controller.

In embodiments, images detected by sensors 24, 124, or 224 are evaluated by the controller. In embodiments, the controller is microprocessor-based and includes a non-transitory computer-readable medium. The non-transitory computer readable medium includes processing instructions stored therein, the processing instructions being executable by the microprocessor of the controller to evaluate the detected image and display surface under test. Determine the level of imperfection. A non-transitory computer-readable medium, or memory, may be random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (such as EPROM, EEPROM, or flash memory), or any other capable of storing information. tangible medium of expression.

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

At step 310, an incoherent optical signal is emitted, for example by applying electrical power to the light source. In the exemplary embodiment, the light signal is an LED signal coming from one of light sources 12, 112, or 212. FIG. At step 320, the incoherent optical signal passes through a beam splitter, such as polarizing beam splitter 16, or non-polarizing beam splitter 116 or 216, to produce a first optical signal and a second optical signal angled with respect to each other. produce. In one exemplary embodiment, the first and second optical signals may be angled 90° with respect to each other and split approximately 50/50, thereby Each will be of equal or substantially equal intensity. Light passing straight through a polarizing beam splitter is linearly polarized in a first direction and is referred to herein as P-polarized light. In the case of non-polarizing beamsplitters, the light is not polarized by the beamsplitter.

At step 330, at least a portion of the incoherent optical signal passes through a collimation lens to create a collimated optical signal. In some systems made according to the present disclosure, such as system 10, this collimation step may occur before the incoherent optical signal enters the beamsplitter. In other systems made according to the present disclosure, such as systems 110, 110', and 210, this step may occur after the optical signal has passed through or been reflected by the beam splitter. Therefore, in some cases only a portion of the incoherent optical signal may pass through the collimation lens.

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

At step 350, the collimated light signal reflects off a surface to be evaluated, such as a reflective surface of display module 50 or 250, to produce a reflected light signal. This reflected light signal is sensed, such as by a sensor such as sensor 24, 124, or 224, to produce a sensed image. In step 370, this sensed image is used for contrast evaluation to determine the presence and magnitude of unevenness in the surface being evaluated.

In one embodiment, display module 50, 250 may be a mobile phone, tablet, or other handheld display device, and system 10, 110, 110', or 210 evaluates the operator interface of the mobile phone or tablet. used to For example, FIGS. 6A and 6B show a mobile phone 400 that can be substituted for display module 50 or 250 (depending on whether phone 400 has a nominally flat or nominally curved user interface).

As shown in FIG. 6A, mobile phone 400 includes back cover 410 . The bottom shell 420 protects a circuit board 425 that is connected with the face shell 430 and configured to provide functionality to the mobile phone 400 . Bottom shell 420 is configured to support battery 415 and is further configured to connect with back cover 410 . Face shell 430 is configured to connect with and support display module 440 . When fully assembled, display module 440 includes display layer 470 and cover glass/touch panel 450a. The cover glass/touch panel 450a is configured as a transparent material or transparent optical material 450. As shown in FIG. When all of the various components are connected, the mobile phone 400 is configured in a convenient container suitable for manual handling. A tablet may be configured similar to phone 400, except for larger overall dimensions.

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, circular polarizer 460 may be integrated into display layer 470 , as indicated by the dashed outline surrounding both display layer 470 and circular polarizer 460 . The display layer 470 is configured to provide a visual interface to a corresponding user by displaying images viewable by the user. Display layer 470 may include one or more additional layers as needed or desired for a particular application. Various techniques are used to construct the display layer 470 . Display layer 470 is typically configured as pixels that provide colored light that is visible to a user. These technologies include liquid crystal displays (LCDs), light emitting diodes (LEDs), organic light emitting diodes (OLEDs), and the like. Cover glass/touch panel 450 a is positioned adjacent to display layer 470 or circular polarizer 460 associated with display layer 470 . The cover glass/touch panel 450a is configured as a user interface. A user may interact with mobile phone 400 and/or provide input control by using a stylus or one or more fingers to touch glass or panel 450a.

Other displays of display module 440 and/or transparent optical material 450, such as display screens, television screens, computer monitors, tablet devices, integrated display screens (e.g., integrated into vehicle dashes, desk surfaces, panels, etc.), portable communication devices, etc. use is contemplated.

In particular, uniformity of top surface 451 of cover glass/touch panel 450a and top surface 471 of display layer 470 is desirable for an optimal visual experience for the user. Embodiments of the present disclosure, including the systems 10, 110, 110′, and 210 described in detail above, provide for flatness on the top surface 451 of the cover glass 450a or other transparent material and display layer 470 or other reflective material. is configured to detect and/or measure flatness at the top surface 471 of the .

While this invention has been described as having exemplary designs, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from this disclosure as are within the known or customary practice of the art to which this invention pertains, and which fall within the scope of the appended claims. .

Claims (19)

An imaging system,
an incoherent light source that emits an incoherent optical signal;
a collimation lens positioned to receive the incoherent light signal and emitting a collimated light signal;
a sensor lens defining a sensor lens plane positioned substantially perpendicular to a direction of travel of the incoherent light signal emitted from the incoherent light source and positioned to receive reflections of the collimated light signal; a sensor, and
a polarizer disposed between the incoherent light source and the sensor;
a display module having a surface to be evaluated defining a plane of the evaluation surface and positioned such that the plane of the evaluation surface is substantially perpendicular to the direction of travel of the collimated light signal; imaging system. 2. The sensor lens plane of claim 1, wherein the sensor lens plane is substantially parallel to the plane of the evaluation plane and the direction of travel of the incoherent optical signal is substantially parallel to the plane of the evaluation plane. imaging system. 2. The sensor lens plane of claim 1, wherein the sensor lens plane is substantially perpendicular to the plane of the evaluation plane and the direction of travel of the incoherent optical signal is substantially perpendicular to the plane of the evaluation plane. The imaging system described. 2. The imaging system of claim 1, wherein the evaluated surface is a substantially flat surface, whereby the image sensed by the sensor includes a contrast indication of the non-flatness of the evaluated surface. The evaluated surface is a curved surface, further comprising a cylindrical lens having a curvature corresponding to the curved surface, whereby the image sensed by the sensor is an imperfection in the curvature of the evaluated surface. 3. The imaging system of claim 1, including a gender contrast display. 2. The imaging system of Claim 1, wherein the sensor lens comprises an aperture. further comprising a beam splitter positioned to split the incoherent optical signal into a first optical signal and a second optical signal, the first optical signal being angled with respect to the second optical signal; 10. The imaging system of claim 1, attached. The polarizer is
a first linear polarizer disposed between the incoherent light source and the beam splitter, the beam splitter comprising a non-polarizing beam splitter;
8. The imaging system of claim 7, comprising a second linear polarizer disposed between said sensor and said beamsplitter. 8. The imaging system of claim 7, wherein said beam splitter and said polarizer are combined as a polarizing beam splitter. 10. The imaging system of Claim 9, further comprising a collection lens disposed between said polarizing beam splitter and said sensor. 11. The imaging system of Claim 10, wherein the sensor lens comprises one of an aperture and a knife edge. 2. The imaging system of Claim 1, wherein the incoherent light signal is emitted by a light emitting diode. A method for evaluating imperfections in an evaluated surface of a display module, 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 with respect to the second optical signal; are, steps and
passing at least a portion of the incoherent optical signal through a collimation lens to produce a collimated optical signal;
reflecting the collimated light signal off the evaluated surface of the display module to produce a reflected light signal, the evaluated surface being substantially perpendicular to the direction of travel of the collimated light signal; defining a plane of an evaluation plane;
and C. sensing a reflected light signal at a sensor to produce a sensed image. 14. The method of claim 13, further comprising evaluating contrast in the sensed image to determine the presence and magnitude of surface unevenness in the evaluated surface. The surface to be evaluated is a curved surface, and the method comprises:
further comprising passing the collimated light signal through a cylindrical lens to produce the modified collimated light signal;
reflecting comprises reflecting the modified collimated optical signal off the curved surface to be evaluated;
15. The method of claim 14, wherein assessing contrast comprises determining the presence and extent of imperfections in curvature of the curved assessed surface. the surface to be evaluated is a substantially flat surface;
15. The method of claim 14, wherein assessing contrast comprises determining the presence and extent of non-planarity in the substantially planar surface. 14. The method of claim 13, further comprising polarizing at least one of the incoherent optical signal, a portion of the incoherent optical signal, and the collimated optical signal. Sensing the reflected light signal comprises:
passing the reflected optical signal through one of the apertures;
and passing the reflected light signal over a knife edge. positioning the collimation lens substantially perpendicular to at least a portion of the incoherent optical signal;
14. The method of claim 13, further comprising positioning the surface to be evaluated substantially parallel to the collimation lens.

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